The difference between three equals sign = = and two equals sign = =

The two equals sign is the only one that determines whether the value is equal;

The three equals sign is the judgment value is equal, and the judgment type is the same;

Example:

$str = "1";

$num = 1;

if ($str = = $num) {

Print_r (' true ');

}else{

Print_r (' false ');

}

if ($str = = = $num) {

Print_r (' true ');

}else{

Print_r (' false ');

}

The running result of the program is:

TrueFalse

Since the first if is executed, PHP converts the $STR string type into a numeric type, compared to $num;

When executing the second if, although the values are compared equal, they can be of unequal type, so they return false;

The difference between three equals sign = = and two equals sign = =