Use phpdbg to debug php programs

PHPDBG is a PHP SAPI module that can control the PHP operating environment without modifying the code and without affecting performance.

Can be used in PHP5.4 and other used in the previous version. In PHP5.6 and above,

functions will be internally integrated

• Single-step debugging
• Flexible breakpoint methods (class methods, functions, files: Line, memory address, opcode)
• You can directly call php's eval
• You can view the currently executed code
• User space API (userland/user space)
• Convenient integration
• Support specified php configuration file
• JIT global variables
• readline support (optional), terminal operation is more convenient
• Remote debug, Using java GUI
• Easy to operate (see help for details)

Installation

If it is PHP56

cd /usr/src/php-src/sapi git clone https://github.com/krakjoe/phpdbg cd ../ ./buildconf --force ./config.nice make -j8 make install-phpdbg

PHP56, just enable phpdbg directly

Note: --with-readline for phpdbg to support history, autocompletion, tab-listing etc

phpdbginit

can be enabled in the php configurationSetting up your debugging session automatically

phpdbg -imy.phpdbginit

the setup of auto completionIn addition,.phpdbginitcan contain embedded code, allowing, for example

• the registration of functions
• the acquisition and pre-compilation of code
• bootstrapping a web application

The default .phpdbginit

########################################################## # .phpdbginit # # Lines starting with # are ignored # Code must start and end with <: and :> respectively ########################################################## # Place initialization commands one per line ########################################################## # exec sapi/phpdbg/test.php ########################################################## # Embedding code in .phpdbginit ########################################################## <: /* If readline is loaded, you might want to setup completion: */ if (function_exists('readline_completion_function')) { readline_completion_function(function(){ return array_merge( get_defined_functions()['user'], array_keys(get_defined_constants()) ); }); } :> ########################################################## # Now carry on initializing phpdbg ... ########################################################## # R my_debugging_function ########################################################## # PHP has many functions that might be useful # ... you choose ... ########################################################## # R touch # R unlink # R scandir # R glob ########################################################## # Remember: *you have access to the shell* ########################################################## # The output of registered function calls is not, # by default, very pretty (unless you implement # and register a new implementation for phpdbg) # The output of shell commands will usually be more # readable on the console ########################################################## # TLDR; if you have a good shell, use it ... ##########################################################　

Check the version number

[root@localhost ~]# php -v PHP 5.6.16 (cli) (built: Dec 8 2015 09:10:23) (DEBUG) Copyright (c) 1997-2015 The PHP Group Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies with Xdebug v2.3.3, Copyright (c) 2002-2015, by Derick Rethans [root@localhost ~]# phpdbg -V phpdbg 0.4.0 (built: Dec 8 2015 09:10:43) PHP 5.6.16, Copyright (c) 1997-2015 The PHP Group Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies with Xdebug v2.3.3, Copyright (c) 2002-2015, by Derick Rethans

Check help

[root@localhost ~]# phpdbg [Welcome to phpdbg, the interactive PHP debugger, v0.4.0] To get help using phpdbg type "help" and press enter [Please report bugs to ] phpdbg> help phpdbg is a lightweight, powerful and easy to use debugging platform for PHP5.4+ It supports the following commands: Information list list PHP source info displays information on the debug session print show opcodes frame select a stack frame and print a stack frame summary back shows the current backtrace help provide help on a topic Starting and Stopping Execution exec set execution context run attempt execution step continue execution until other line is reached continue continue execution until continue execution up to the given location finish continue up to end of the current execution frame leave continue up to end of the current execution frame and halt after the calling instruction break set a breakpoint at the specified target watch set a watchpoint on $variable clear clear one or all breakpoints clean clean the execution environment Miscellaneous set set the phpdbg configuration source execute a phpdbginit script register register a phpdbginit function as a command alias sh shell a command ev evaluate some code quit exit phpdbg Type help  or (help alias) to get detailed help on any of the above commands, for example help list or h l. Note that help will also match partial commands if unique (and list out options if not unique), so help clea will give help on the clean command, but help cl will list the summary for clean and clear. Type help aliases to show a full alias list, including any registered phpdginit functions Type help syntax for a general introduction to the command syntax. Type help options for a list of phpdbg command line options. Type help phpdbginit to show how to customise the debugger environment. phpdbg> help list Command: list Alias: l lists some code The list command displays source code for the given argument. The target type is specficied by a second subcommand keyword: Type Alias Purpose lines l List N lines from the current execution point func f List the complete source for a specified function method m List the complete source for a specified class::method class c List the complete source for a specified class Note that the context of lines, func and method can be determined by parsing the argument, so these subcommands are optional. However, you must specify the class keyword to list off a class. Examples phpdbg> list 2 phpdbg> l l 2 List the next 2 lines from the current file phpdbg> list my_function phpdbg> l f my_function List the source of the function my_function phpdbg> list func .mine phpdbg> l f .mine List the source of the method mine from the active class in scope phpdbg> list m my::method phpdbg> l my::method List the source of my::method phpdbg> list c myClass phpdbg> l c myClass List the source of myClass Note that functions and classes can only be listed if the corresponding classes and functions table in the Zend executor has a corresponding entry. You can use the compile command to populate these tables for a given execution context. phpdbg> help break Command: break Alias: b set breakpoint Breakpoints can be set at a range of targets within the execution environment. Execution will be paused if the program flow hits a breakpoint. The break target can be one of the following types: Target Alias Purpose at A specify breakpoint by location and condition del d delete breakpoint by breakpoint identifier number Break at takes two arguments. The first is any valid target. The second is a valid PHP expression which will trigger the break in execution, if evaluated as true in a boolean context at the specified target. Note that breakpoints can also be disabled and re-enabled by the set break command. Examples phpdbg> break test.php:100 phpdbg> b test.php:100 Break execution at line 100 of test.php phpdbg> break 200 phpdbg> b 200 Break execution at line 200 of the currently PHP script file phpdbg> break \mynamespace\my_function phpdbg> b \mynamespace\my_function Break execution on entry to \mynamespace\my_function phpdbg> break classX::method phpdbg> b classX::method Break execution on entry to classX::method phpdbg> break 0x7ff68f570e08 phpdbg> b 0x7ff68f570e08 Break at the opline at the address 0x7ff68f570e08 phpdbg> break my_function#14 phpdbg> b my_function#14 Break at the opline #14 of the function my_function phpdbg> break \my\class::method#2 phpdbg> b \my\class::method#2 Break at the opline #2 of the method \my\class::method phpdbg> break test.php:#3 phpdbg> b test.php:#3 Break at opline #3 in test.php phpdbg> break if $cnt > 10 phpdbg> b if $cnt > 10 Break when the condition ($cnt > 10) evaluates to true phpdbg> break at phpdbg::isGreat if $opt == 'S' phpdbg> break @ phpdbg::isGreat if $opt == 'S' Break at any opcode in phpdbg::isGreat when the condition ($opt == 'S') is true phpdbg> break at test.php:20 if !isset($x) Break at every opcode on line 20 of test.php when the condition evaluates to true phpdbg> break ZEND_ADD phpdbg> b ZEND_ADD Break on any occurence of the opcode ZEND_ADD phpdbg> break del 2 phpdbg> b ~ 2 Remove breakpoint 2 Note: Conditional breaks are costly in terms of runtime overhead. Use them only when required as they significantly slow execution. Note: An address is only valid for the current compilation. phpdbg> help watch Command: watch Alias: w set watchpoint Sets watchpoints on variables as long as they are defined Passing no parameter to watch, lists all actually active watchpoints Format for $variable $var Variable $var $var[] All array elements of $var $var-> All properties of $var $var->a Property $var->a $var[b] Array element with key b in array $var Subcommands of watch: Type Alias Purpose array a Sets watchpoint on array/object to observe if an entry is added or removed recursive r Watches variable recursively and automatically adds watchpoints if some entry is added to an array/object delete d Removes watchpoint Note when recursive watchpoints are removed, watchpoints on all the children are removed too Examples phpdbg> watch List currently active watchpoints phpdbg> watch $array phpdbg> w $array Set watchpoint on $array phpdbg> watch recursive $obj-> phpdbg> w r $obj-> Set recursive watchpoint on $obj-> phpdbg> watch delete $obj->a phpdbg> w d $obj->a Remove watchpoint $obj->a Technical note: If using this feature with a debugger, you will get many segmentation faults, each time when a memory page containing a watched address is hit. You then you can continue, phpdbg will remove the write protection, so that the program can continue. If phpdbg could not handle that segfault, the same segfault is triggered again and this time phpdbg will abort.

These help documents are enough

Why is the output of the sample code testb and testa like this?

 0){ $y = $x --; if($arr[$x] < $arr[$y]){ $z = $len; while($arr[$x] > $arr[$z]){ $z--; } list($arr[$x],$arr[$z]) = array($arr[$z],$arr[$x]); for($i=$len;$i>$y;$i--,$y++){ list($arr[$i],$arr[$y]) = array($arr[$y],$arr[$i]); } $x = $len; $rs[] = $arr; } } return $rs; } } $s = new test(); $resa = $s->testa(); $resb = $s->testb(); $resc = $s->allsort([1,2,3]); echo $resa,"\n",$resb,"\n"; #print_r($resb);

Start debugging

[root@localhost ~]# phpdbg -e kk.php [Welcome to phpdbg, the interactive PHP debugger, v0.4.0] To get help using phpdbg type "help" and press enter [Please report bugs to ] [Attempting compilation of /root/kk.php] [Success]

View the opcode of some current classes

phpdbg> p c test [User Class: test] Methods (4): L7-13 test::testa() /root/kk.php L7 0xb77b553c ZEND_EXT_NOP    L9 0xb77b5558 ZEND_EXT_STMT    L9 0xb77b5574 ZEND_ASSIGN $a C0 @0 L10 0xb77b5590 ZEND_EXT_STMT    L10 0xb77b55ac ZEND_ASSIGN_REF $b $a @1 L11 0xb77b55c8 ZEND_EXT_STMT    L11 0xb77b55e4 ZEND_PRE_INC $a  @2 L11 0xb77b5600 ZEND_ADD C1 @2 @3 L11 0xb77b561c ZEND_PRE_INC $a  @4 L11 0xb77b5638 ZEND_ADD @3 @4 @5 L11 0xb77b5654 ZEND_RETURN @5   L13 0xb77b5670 ZEND_EXT_STMT    L13 0xb77b568c ZEND_RETURN C2   L15-21 test::testb() /root/kk.php L15 0xb77b656c ZEND_EXT_NOP    L17 0xb77b6588 ZEND_EXT_STMT    L17 0xb77b65a4 ZEND_ASSIGN $a C0 @0 L18 0xb77b65c0 ZEND_EXT_STMT    L18 0xb77b65dc ZEND_ASSIGN_REF $b $a @1 L19 0xb77b65f8 ZEND_EXT_STMT    L19 0xb77b6614 ZEND_PRE_INC $a  @2 L19 0xb77b6630 ZEND_PRE_INC $a  @3 L19 0xb77b664c ZEND_ADD @2 @3 @4 L19 0xb77b6668 ZEND_RETURN @4   L21 0xb77b6684 ZEND_EXT_STMT    L21 0xb77b66a0 ZEND_RETURN C1   L23-27 test::convert() /root/kk.php L23 0xb77b66ec ZEND_EXT_NOP    L23 0xb77b6708 ZEND_RECV   $size L25 0xb77b6724 ZEND_EXT_STMT    L25 0xb77b6740 ZEND_INIT_ARRAY C0  @0 L25 0xb77b675c ZEND_ADD_ARRAY_ELEMENT C1  @0 L25 0xb77b6778 ZEND_ADD_ARRAY_ELEMENT C2  @0 L25 0xb77b6794 ZEND_ADD_ARRAY_ELEMENT C3  @0 L25 0xb77b67b0 ZEND_ADD_ARRAY_ELEMENT C4  @0 L25 0xb77b67cc ZEND_ADD_ARRAY_ELEMENT C5  @0 L25 0xb77b67e8 ZEND_ASSIGN $unit @0 @1 L26 0xb77b6804 ZEND_EXT_STMT    L26 0xb77b6820 ZEND_BEGIN_SILENCE   @2 L26 0xb77b683c ZEND_EXT_FCALL_BEGIN    L26 0xb77b6858 ZEND_EXT_FCALL_BEGIN    L26 0xb77b6874 ZEND_SEND_VAL C6   L26 0xb77b6890 ZEND_EXT_FCALL_BEGIN    L26 0xb77b68ac ZEND_EXT_FCALL_BEGIN    L26 0xb77b68c8 ZEND_SEND_VAR $size   L26 0xb77b68e4 ZEND_SEND_VAL C7   L26 0xb77b6900 ZEND_DO_FCALL C8  @3 L26 0xb77b691c ZEND_EXT_FCALL_END    L26 0xb77b6938 ZEND_SEND_VAR_NO_REF @3   L26 0xb77b6954 ZEND_DO_FCALL C9  @4 L26 0xb77b6970 ZEND_EXT_FCALL_END    L26 0xb77b698c ZEND_ASSIGN $i @4 @5 L26 0xb77b69a8 ZEND_SEND_VAR_NO_REF @5   L26 0xb77b69c4 ZEND_DO_FCALL C10  @6 L26 0xb77b69e0 ZEND_EXT_FCALL_END    L26 0xb77b69fc ZEND_DIV $size @6 @7 L26 0xb77b6a18 ZEND_SEND_VAL @7   L26 0xb77b6a34 ZEND_SEND_VAL C11   L26 0xb77b6a50 ZEND_DO_FCALL C12  @8 L26 0xb77b6a6c ZEND_EXT_FCALL_END    L26 0xb77b6a88 ZEND_END_SILENCE @2   L26 0xb77b6aa4 ZEND_CONCAT @8 C13 @9 L26 0xb77b6ac0 ZEND_FETCH_DIM_R $unit $i @10 L26 0xb77b6adc ZEND_CONCAT @9 @10 @11 L26 0xb77b6af8 ZEND_RETURN @11   L27 0xb77b6b14 ZEND_EXT_STMT    L27 0xb77b6b30 ZEND_RETURN C14   L29-54 test::allsort() /root/kk.php L29 0xb77b818c ZEND_EXT_NOP    L29 0xb77b81a8 ZEND_RECV   $arr L30 0xb77b81c4 ZEND_EXT_STMT    L30 0xb77b81e0 ZEND_EXT_FCALL_BEGIN    L30 0xb77b81fc ZEND_SEND_REF $arr   L30 0xb77b8218 ZEND_DO_FCALL C0  @0 L30 0xb77b8234 ZEND_EXT_FCALL_END    L31 0xb77b8250 ZEND_EXT_STMT    L31 0xb77b826c ZEND_EXT_FCALL_BEGIN    L31 0xb77b8288 ZEND_SEND_VAR $arr   L31 0xb77b82a4 ZEND_DO_FCALL C1  @1 L31 0xb77b82c0 ZEND_EXT_FCALL_END    L31 0xb77b82dc ZEND_SUB @1 C2 @2 L31 0xb77b82f8 ZEND_ASSIGN $len @2 @3 L32 0xb77b8314 ZEND_EXT_STMT    L32 0xb77b8330 ZEND_INIT_ARRAY   @4 L32 0xb77b834c ZEND_ASSIGN $rs @4 @5 L33 0xb77b8368 ZEND_EXT_STMT    L33 0xb77b8384 ZEND_ASSIGN_DIM $rs  @6 L33 0xb77b83a0 UNKNOWN $arr @7  L34 0xb77b83bc ZEND_EXT_STMT    L34 0xb77b83d8 ZEND_ASSIGN $x $len @8 L36 0xb77b83f4 ZEND_EXT_STMT    L36 0xb77b8410 ZEND_IS_SMALLER C3 $x @9 L36 0xb77b842c ZEND_JMPZ @9 J86  L37 0xb77b8448 ZEND_EXT_STMT    L37 0xb77b8464 ZEND_POST_DEC $x  @10 L37 0xb77b8480 ZEND_ASSIGN $y @10 @11 L38 0xb77b849c ZEND_EXT_STMT    L38 0xb77b84b8 ZEND_FETCH_DIM_R $arr $x @12 L38 0xb77b84d4 ZEND_FETCH_DIM_R $arr $y @13 L38 0xb77b84f0 ZEND_IS_SMALLER @12 @13 @14 L38 0xb77b850c ZEND_JMPZ @14 J85  L39 0xb77b8528 ZEND_EXT_STMT    L39 0xb77b8544 ZEND_ASSIGN $z $len @15 L40 0xb77b8560 ZEND_EXT_STMT    L40 0xb77b857c ZEND_FETCH_DIM_R $arr $x @16 L40 0xb77b8598 ZEND_FETCH_DIM_R $arr $z @17 L40 0xb77b85b4 ZEND_IS_SMALLER @17 @16 @18 L40 0xb77b85d0 ZEND_JMPZ @18 J44  L41 0xb77b85ec ZEND_EXT_STMT    L41 0xb77b8608 ZEND_POST_DEC $z  @19 L41 0xb77b8624 ZEND_FREE @19   L42 0xb77b8640 ZEND_JMP J36 L43 0xb77b865c ZEND_EXT_STMT    L43 0xb77b8678 ZEND_FETCH_DIM_R $arr $z @20 L43 0xb77b8694 ZEND_INIT_ARRAY @20  @21 L43 0xb77b86b0 ZEND_FETCH_DIM_R $arr $x @22 L43 0xb77b86cc ZEND_ADD_ARRAY_ELEMENT @22  @21 L43 0xb77b86e8 ZEND_FETCH_DIM_TMP_VAR @21 C4 @23 L43 0xb77b8704 ZEND_ASSIGN_DIM $arr $z @24 L43 0xb77b8720 UNKNOWN @23 @25  L43 0xb77b873c ZEND_FETCH_DIM_TMP_VAR @21 C5 @26 L43 0xb77b8758 ZEND_ASSIGN_DIM $arr $x @27 L43 0xb77b8774 UNKNOWN @26 @28  L43 0xb77b8790 ZEND_FREE @21   L45 0xb77b87ac ZEND_EXT_STMT    L45 0xb77b87c8 ZEND_ASSIGN $i $len @29 L45 0xb77b87e4 ZEND_IS_SMALLER $y $i @30 L45 0xb77b8800 ZEND_EXT_STMT    L45 0xb77b881c ZEND_JMPZNZ @30 J79 or J66  L45 0xb77b8838 ZEND_POST_DEC $i  @31 L45 0xb77b8854 ZEND_FREE @31   L45 0xb77b8870 ZEND_POST_INC $y  @32 L45 0xb77b888c ZEND_FREE @32   L45 0xb77b88a8 ZEND_JMP J58 L46 0xb77b88c4 ZEND_EXT_STMT    L46 0xb77b88e0 ZEND_FETCH_DIM_R $arr $y @33 L46 0xb77b88fc ZEND_INIT_ARRAY @33  @34 L46 0xb77b8918 ZEND_FETCH_DIM_R $arr $i @35 L46 0xb77b8934 ZEND_ADD_ARRAY_ELEMENT @35  @34 L46 0xb77b8950 ZEND_FETCH_DIM_TMP_VAR @34 C6 @36 L46 0xb77b896c ZEND_ASSIGN_DIM $arr $y @37 L46 0xb77b8988 UNKNOWN @36 @38  L46 0xb77b89a4 ZEND_FETCH_DIM_TMP_VAR @34 C7 @39 L46 0xb77b89c0 ZEND_ASSIGN_DIM $arr $i @40 L46 0xb77b89dc UNKNOWN @39 @41  L46 0xb77b89f8 ZEND_FREE @34   L47 0xb77b8a14 ZEND_JMP J61 L48 0xb77b8a30 ZEND_EXT_STMT    L48 0xb77b8a4c ZEND_ASSIGN $x $len @42 L49 0xb77b8a68 ZEND_EXT_STMT    L49 0xb77b8a84 ZEND_ASSIGN_DIM $rs  @43 L49 0xb77b8aa0 UNKNOWN $arr @44  L50 0xb77b8abc ZEND_JMP J85 L52 0xb77b8ad8 ZEND_JMP J23 L53 0xb77b8af4 ZEND_EXT_STMT    L53 0xb77b8b10 ZEND_RETURN $rs   L54 0xb77b8b2c ZEND_EXT_STMT    L54 0xb77b8b48 ZEND_RETURN C8   phpdbg>

Add breakpoints and start debugging

phpdbg> b test::testa [Breakpoint #0 added at test::testa] phpdbg> b test::testb [Breakpoint #1 added at test::testb] phpdbg> b 0xb77b6614 [Breakpoint #2 added at 0xb77b6614] phpdbg> b 0xb77b6630 [Breakpoint #3 added at 0xb77b6630]

Run and view the code

phpdbg> r [Breakpoint #0 in test::testa() at /root/kk.php:7, hits: 1] 00006: >00007: public function testa(){ 00008: 00009: $a=1; phpdbg> l test::testa 00007: public function testa(){ 00008: 00009: $a=1; 00010: $b = &$a; 00011: return 0 + (++$a) + (++$a); 00012: 00013: } 00014: phpdbg> p s [Stack in test::testa()] L7-13 test::testa() /root/kk.php L7 0xb77b553c ZEND_EXT_NOP    L9 0xb77b5558 ZEND_EXT_STMT    L9 0xb77b5574 ZEND_ASSIGN $a C0 @0 L10 0xb77b5590 ZEND_EXT_STMT    L10 0xb77b55ac ZEND_ASSIGN_REF $b $a @1 L11 0xb77b55c8 ZEND_EXT_STMT    L11 0xb77b55e4 ZEND_PRE_INC $a  @2 L11 0xb77b5600 ZEND_ADD C1 @2 @3 L11 0xb77b561c ZEND_PRE_INC $a  @4 L11 0xb77b5638 ZEND_ADD @3 @4 @5 L11 0xb77b5654 ZEND_RETURN @5   L13 0xb77b5670 ZEND_EXT_STMT    L13 0xb77b568c ZEND_RETURN C2  

Continue execution

Like gdb, the continue execution command of phpdbg is also continue, the abbreviation is c

View breakpoint

phpdbg> info b ------------------------------------------------ Method Breakpoints: #0 test::testa #1 test::testb ------------------------------------------------ Opline Breakpoints: #2 0xb77b6614 #3 0xb77b6630

eval operation

Can execute arbitrary PHP code

We can see the difference between testa and testb in the above example

L7-13 test::testa() /root/kk.php L11 0xb77b55e4 ZEND_PRE_INC $a  @2 L11 0xb77b5600 ZEND_ADD C1 @2 @3 L11 0xb77b561c ZEND_PRE_INC $a  @4 L11 0xb77b5638 ZEND_ADD @3 @4 @5 L15-21 test::testb() /root/kk.php L19 0xb77b6614 ZEND_PRE_INC $a  @2 L19 0xb77b6630 ZEND_PRE_INC $a  @3 L19 0xb77b664c ZEND_ADD @2 @3 @4

The difference is that ZEND_PRE_INC is a different opcode. This opcode is $a

testb When the reference exists, $a is incremented twice first, and then added, so the result is 6. This should be a problem with PHP itself.

This tool is much richer than vld, and PHP will become more and more The more powerful.

Recommended related PHP video tutorials:"PHP Video Tutorial"

The above is the detailed content of Use phpdbg to debug php programs. For more information, please follow other related articles on the PHP Chinese website!