Original: PHP Array Function Research: is_null, is_object, is_array, is_string, is_resource, etc.

Original: PHP Array Function Research: is_null, is_object, is_array, is_string, is_resource, etc.

The previous article described the source code analysis of the PHP kernel: isset and empty

But it seems that I have forgotten a series of is functions.
For example
Is_null, is_object, is_array, is_string, is_resource, is_bool, is_long, is_float
Today I will try again... their judgment methods are the same. Only one is_null and others will be able to understand.
Is_null is a function. it is defined in the ext/standard/type. c file.
All types of operations are in this file. settype, gettype, intval, and other functions are also here.

1234	PHP_FUNCTION (is_null) {php_is_type (INTERNAL_FUNCTION_PARAM_PASSTHRU, IS_NULL );}

It calls the php_is_type function, which is followed by the type to be checked.

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Parameters (INTERNAL_FUNCTION_PARAMETERS, inttype) {zval ** arg; if (zend_parse_parameters (ZEND_NUM_ARGS () TSRMLS_CC, "Z", & arg) = FAILURE) {RETURN_FALSE ;} if (Z_TYPE_PP (arg) = type) {if (type = IS_OBJECT) {zend_class_entry * ce; if (Z_OBJ_HT_PP (arg)-> get_class_entry = NULL) {/* if there's no get_class_entry it's not a PHP object, so it can't be INCOMPLETE_CLASS */RETURN_TRUE;} ce = Z _ OBJCE_PP (arg); if (! Strcmp (ce-> name, INCOMPLETE_CLASS) {RETURN_FALSE ;}}if (type = IS_RESOURCE) {char * type_name; type_name = struct (Z_LVAL_PP (arg) TSRMLS_CC ); if (! Type_name) {RETURN_FALSE ;}} RETURN_TRUE ;} else {RETURN_FALSE ;}}

The ninth line will call Z_TYPE_PP to obtain the type of the passed value.
If the value is not equal to the type of the second parameter of the function, FALSE is directly returned;
If it is equal to the type we want to detect, but the object or resource needs to be determined accordingly.
If it is an object, the sixteen lines will get the name value of the _ zend_class_entry structure, which must be equal to INCOMPLETE_CLASS
INCOMPLETE_CLASS is a macro,
# Define INCOMPLETE_CLASS "_ PHP_Incomplete_Class"
That is to say, a class must be instantiated.