Usage of echo(), print(), print_r() in php_PHP tutorial

From my understanding of the functions echo(), print(), and print_r(), echo can input string variable constants. Print is similar to echo, but print_r can print arrays while the first two cannot. Below Let me introduce the usage and differences between the three of them in detail.

Echo is a PHP statement, print and print_r are functions. Statements have no return value, but functions can have return values ​​(even if they are useless)
print() can only print out the value of simple type variables (such as int, string)
print_r() can print out the value of complex type variables (such as arrays, objects)
echo outputs one or more strings

echo — Output one or more strings
Descrīption
void echo ( string arg1 [, string ...] ) //The return value is empty

The code is as follows	Copy code
echo "Hello","Friend";  代码如下 复制代码 echo "你好","朋友";

print – output a string

Descrīption

int print (string arg)//The return value is an integer

The code is as follows	Copy code
代码如下 复制代码   print "你好朋友"; print "Hello friend";

You can perform the following operations

代码如下	复制代码
$name=print "nihao n"; $str = 'test print value is'.$name; eval("$print="$str";"); echo $print;

The code is as follows	Copy code
$name=print "nihao n"; $str = 'test print value is'.$name; eval("$print="$str";"); echo $print;

print_r — Print human-readable information about a variable. bool print_r (mixed expression [, bool return] ) //The return value is of Boolean type, and the parameters are of mix type, which can be strings, integers, arrays, and object classes. print_r() displays easy-to-understand information about a variable. If a string, integer, or float is given, the variable value itself is printed. If an array is given, the keys and elements will be displayed in a certain format. object is similar to an array.

print_r() will move the array pointer to the end. You can print_r(str);

print_r(int);

print_r(array);

print_r(obj);

Let’s give examples one by one

Four ways to output strings. echo

print()

printf()

print_r()

echo

代码如下	复制代码
if (!print("Hello, World")){    die("you are not listening to me"); }

Multiple values ​​can be output at one time, separated by commas. echo is a language construct, not a real function, so it cannot be used as part of an expression. The syntax is correct: echo "Hello", "World"; Syntax error: echo ("Hello", "World"); print() The function print() prints a value (its argument) and returns true if the string is successfully displayed, false otherwise. For example,

The code is as follows	Copy code
if (!print("Hello, World")){ die("you are not listening to me"); }

printf()
printf() is derived from printf() in C language. This function outputs a formatted string.
Syntax: printf(format,arg1,arg2,arg++)
format specifies the string and how to format the variables in it;
Arguments arg1, arg2, ++, etc. are inserted into the main string at the percent sign (%) symbol. This function is executed step by step. At the first % sign, arg1 is inserted, at the second % sign, arg2, and so on.
Example: ?php

The code is as follows  代码如下 复制代码 $str = "Hello"; $number = 123; printf("%s world. Day number %u",$str,$number); ?> #Results====== Hello world. Day number 123

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$str = "Hello";  代码如下 复制代码 $number = 123; printf("With 2 decimals: %1$.2fbr />With no decimals: %1$u",$number); ?> #Result With 2 decimals: 123.00 With no decimals: 123 $number = 123; printf("%s world. Day number %u",$str,$number);  代码如下 复制代码 $a = array('name' => 'Fred', 'age' => '15', 'wife' => 'Wilma'); print_r($a); Output： Array {    [name] => Fred     [age] => 15     [wife] => Wilma } ?> #Results======  代码如下 复制代码 class P {   var $name = 'nat';   // ... } $p = new P; print_r($p); Output: Object { [name] => nat } Hello world. Day number 123

If there are more % symbols than arg arguments, you must use placeholders. The placeholder is inserted after the % sign and consists of a number and "$". See example 3. Example: ?php

The code is as follows

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$number = 123; printf("With 2 decimals: %1$.2fbr />With no decimals: %1$u",$number); ?> #Result With 2 decimals: 123.00 With no decimals: 123 print_r() and var_dump() print_r() can simply print out strings and numbers, while arrays are displayed as a bracketed list of keys and values, starting with Array. For example, The code is as follows Copy code $a = array('name' => 'Fred', 'age' => '15', 'wife' => 'Wilma'); print_r($a); Output: Array { [name] => Fred [age] => 15 [wife] => Wilma } The same goes for objects. For example, The code is as follows Copy code class P { var $name = 'nat'; // ... } $p = new P; print_r($p); Output: Object { [name] => nat } But the results of print_r() outputting Boolean values ​​and NULL are meaningless, because they all print "n". Therefore, using the var_dump() function is more suitable for debugging http://www.bkjia.com/PHPjc/631244.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/631244.htmlTechArticleFrom my understanding of the echo(), print(), print_r() functions, echo can input a string Variable constants, print and echo are similar, but print_r can print arrays but the first two cannot. Below I...