A brief discussion of PHP source code 16: About the array_count_values ​​function

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Brief discussion on PHP source code 10 6: About the array_count_values ​​function

array_count_values

(PHP 4, PHP 5)
array_count_values ​​- Counts the number of occurrences of all values ​​in the array
Description

array array_count_values ​​(array input)

array_count_values() Returns an array that uses the value in the input array as the key name and the number of times the value appears in the input array as the value.

Source program description:
The two comments in the source code explain the implementation of this function

  /* Initialize return array */
    array_init(return_value);     /* Go through input array and add values to the return array */

But there are some details that need to be paid attention to:

1. This function can only recognize strings and numbers, so the program uses statements similar to the following

if (Z_TYPE_PP(entry) == IS_LONG) {} else if (Z_TYPE_PP(entry) == IS_STRING) {} else {
            php_error_docref(NULL TSRMLS_CC, E_WARNING, "Can only count STRING and INTEGER values!");}

2. During the traversal process, first determine whether it does not exist. This judgment process is based on strings and numbers. The numbers are also different, but in the end they are all operations on the hash table.

In the code, the macro zval *data; MAKE_STD_ZVAL(data);
is used to initialize zval in the code. The definition of tracking this macro is as follows:

MAKE_STD_ZVAL(data);==> #define MAKE_STD_ZVAL(zv)                 \    zend.h 586行
    ALLOC_ZVAL(zv); \
    INIT_PZVAL(zv); ==> #define ALLOC_ZVAL(z)    \
    ZEND_FAST_ALLOC(z, zval, ZVAL_CACHE_LIST)    zend_alloc.h 165行 ==> #define ZEND_FAST_ALLOC(p, type, fc_type)    \
    (p) = (type *) emalloc(sizeof(type))                   zend_alloc.h  152行 ==> #define emalloc(size)                        _emalloc((size) ZEND_FILE_LINE_CC ZEND_FILE_LINE_EMPTY_CC)    zend_alloc.h 56行==> ZEND_API void *_emalloc(size_t size ZEND_FILE_LINE_DC ZEND_FILE_LINE_ORIG_DC)      zend_alloc.c 2288行 程序实现
 ==>  #define INIT_PZVAL(z)        \                 zend.h 576行
    (z)->refcount = 1;        \    (z)->is_ref = 0;

EOF

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