PHP equal operator == reference table


1	For more information, tests and examples see this post:	http://gynvael.coldwind.pl/?id=492		(note: this table totally ignores proxy objects)				by Gynvael Coldwind (2013-01-01)
2	op1 → op2 ↓	NULL	BOOL	LONG	DOUBLE	STRING	ARRAY	OBJECT	RESOURCE

3	NULL	always equal	if op1 is FALSE then equal	equal if op1 is 0	equal if op1 evaluates as false in C	converts NULL to STRING "" calls zend_binary_strcmp	equal if array is empty	always not equal	equal if op1 numeric value is 0
4	BOOL	if op2 is FALSE then equal	equal if (LONG)op1-(LONG)op2 is 0	op1 is converted to BOOL like this: if op1 is 0, then FALSE else TRUE then it's compared with op2	op1 is converted to BOOL like this: if op1 evaluates as true in C, it's TRUE else it's FALSE then it's compared with op2	op1 is converted to BOOL like this: if op1 is exactly "0" or empty string, it's FALSE else it's true then it's compared with op2	op1 is converted to BOOL like this: if array is empty, it's FALSE else it's TRUE then it's compared with op2	if op1 has cast_object, then it's cast to BOOL; on failure to cast; it's unequal on success, it's compares as BOOL vs BOOL in case of no cast_object: op2 is cast to LONG, op1 is cast to LONG(1) and a LONG vs LONG comparison is done standard php object will cast object to BOOL(true)	op1 is converted to BOOL like this: if op1 value is 0, then FALSE else TRUE then it's compared with op2
5	LONG	equal if op2 is 0	op2 is converted to BOOL like this: if op2 is 0, then FALSE else TRUE then it's compared with op1	if not op1>op2 and not op1<op2 then equal	op2 is cast to DOUBLE then compared with op1	op1 is converted to LONG or DOUBLE or to LONG(0) if conversion fails then it's compared: - either LONG vs LONG or - op2 is cast to DOUBLE, and it's compared DOUBLE vs DOUBLE	always not equal	if op1 has cast_object, then it's cast to LONG; on failure to cast; it's unequal on success, it's compares as LONG vs LONG in case of no cast_object: op1 is cast to LONG(1) and a LONG vs LONG comparison is done standard php object will cast object to LONG(1) but issue an E_NOTICE	op1 numerical value is used as LONG standard LONG vs LONG comparision follows
6	DOUBLE	equal if op2 evaluates as false in C	op2 is converted to BOOL like this: if op2 evaluates as true in C, it's TRUE else it's FALSE then it's compared with op1	op1 is cast to DOUBLE then compared with op1	equal if op1 == op2	op1 is converted to LONG or DOUBLE or to LONG(0) if conversion fails then it's compared: - either DOUBLE vs DOUBLE or - it's cast to DOUBLE, and it's compared DOUBLE vs DOUBLE	always not equal	if op1 has cast_object, then it's cast to DOUBLE; on failure to cast; it's unequal on success, it's compares as DOUBLE vs DOUBLE in case of no cast_object: op1 is cast to LONG(1), op2 is cast to LONG and a LONG vs LONG comparison is done standard php object will cast object to DOUBLE(1.0) but issue an E_NOTICE	op1 numerical value is used as a LONG standard LONG vs DOUBLE comparison follows
7	STRING	converts NULL to STRING "" calls zend_binary_strcmp	op2 is converted to BOOL like this: if op2 is exactly "0" or empty string, it's FALSE else it's true then it's compared with op1	op2 is converted to LONG or DOUBLE or to LONG(0) if conversion fails then it's compared: - either LONG vs LONG or - op1 is cast to DOUBLE, and it's compared DOUBLE vs DOUBLE	op2 is converted to LONG or DOUBLE or to LONG(0) if conversion fails then it's compared: - either DOUBLE vs DOUBLE or - it's cast to DOUBLE, and it's compared DOUBLE vs DOUBLE	tries to convert both strings into LONG or DOUBLE using is_numeric_string; if successful with no overflows: - compares LONG vs LONG or - compares DOUBLE vs DOUBLE - casts LONG to DOUBLE and compares DOUBLE vs DOUBLE otherwise it falls back to string comparison (equal on exact match)	always not equal	if op1 has cast_object, then it's cast to string; on failure to case, it's unequal on success, a standard STRING vs STRING comparison is done in case no cast_object, op1 is cast to LONG(1), op2 is cast to LONG using is_numeric_string, or, in case of failure, it's cast to LONG(0) a LONG vs LONG comparison is done standard php object will call __tostring PHP method if it exists, or return FAILURE if __tostring returns non-string, a recoverable error is raised, but still the cast succeds returning empty STRING; a STRING vs STRING comparison follows	op2 is converted to LONG or DOUBLE using is_numeric_string, or to LONG 0 if conversion fails; op1 numerical value is used as LONG; then comparision is made same as in DOUBLE vs DOUBLE or LONG vs DOUBLE
8	ARRAY	equal if array is empty	op2 is converted to BOOL like this: if array is empty, it's FALSE else it's true then it's compared with op1	always not equal	always not equal	always not equal	to be equal: keys must match to the byte, but values are deeply compared using ALL THIS again	if op1 has cast_object, then it's cast to ARRAY; on failure to cast; it's unequal on success, it's compares as ARRAY vs ARRAY in case of no cast_object: always unequal standard php object will FAIL to cast to ARRAY	always not equal
9	OBJECT	always not equal	if op2 has cast_object, then it's cast to BOOL; on failure to cast; it's unequal on success, it's compares as BOOL vs BOOL in case of no cast_object: op1 is cast to LONG, op2 is cast to LONG(1) and a LONG vs LONG comparison is done standard php object will cast object to BOOL(true)	if op2 has cast_object, then it's cast to LONG; on failure to cast; it's unequal on success, it's compares as LONG vs LONG in case of no cast_object: op2 is cast to LONG(1) and a LONG vs LONG comparison is done standard php object will cast object to LONG(1) but issue an E_NOTICE	if op2 has cast_object, then it's cast to DOUBLE; on failure to cast; it's unequal on success, it's compares as DOUBLE vs DOUBLE in case of no cast_object: op2 is cast to LONG(1), op1 is cast to LONG and a LONG vs LONG comparison is done standard php object will cast object to DOUBLE(1.0) but issue an E_NOTICE	if op2 has cast_object, then it's cast to string; on failure to case, it's unequal on success, a standard STRING vs STRING comparison is done in case no cast_object, op2 is cast to LONG(1), op1 is cast to LONG using is_numeric_string, or, in case of failure, it's cast to LONG(0) a LONG vs LONG comparison is done standard php object will call __tostring PHP method if it exists, or return FAILURE if __tostring returns non-string, a recoverable error is raised, but still the cast succeds returning empty STRING; a STRING vs STRING comparison follows	if op2 has cast_object, then it's cast to ARRAY; on failure to cast; it's unequal on success, it's compares as ARRAY vs ARRAY in case of no cast_object: always unequal standard php object will FAIL to cast to ARRAY	if objects have the same compare handler: - if it's the same object, equal - else call the compare handler (all this again) else (in PHP 5.4.6): try to convert both objects using cast_object to LONG if no cast_object or it fails, object is converted to LONG(1) then compare objects as LONGs NOTE: DO NOT USE else (in PHP 5.4.10): return not equal NOTE: OK	if op2 has cast_object, then it's cast to RESOURCE; on failure to cast; it's unequal on success, it casts both op1 and op2 to LONG and does a LONG vs LONG comparison in case of no cast_object: op1 is cast to LONG, op2 is cast to LONG(1), and a LONG vs LONG comparison is done standard php object will FAIL to cast to RESOURCE
10	RESOURCE	equal if op2 numeric value is 0	op2 is converted to BOOL like this: if op2 value is 0, then FALSE else TRUE then it's compared with op1	op2 numerical value is used as LONG standard LONG vs LONG comparision follows	op2 numerical value is used as a LONG standard LONG vs DOUBLE comparison follows	op1 is converted to LONG or DOUBLE using is_numeric_string, or to LONG 0 if conversion fails; op2 numerical value is used as LONG; then comparision is made same as in DOUBLE vs DOUBLE or LONG vs DOUBLE	always not equal	if op1 has cast_object, then it's cast to RESOURCE; on failure to cast; it's unequal on success, it casts both op1 and op2 to LONG and does a LONG vs LONG comparison in case of no cast_object: op2 is cast to LONG, op1 is cast to LONG(1), and a LONG vs LONG comparison is done standard php object will FAIL to cast to RESOURCE	op1 and op2 numerical values are compared as LONGs (specific subtypes are ignored, but this doesn't matter since the values are unique id's anyway)