expression

Use identities

not good:

Simple comparison will convert the string into an integer

$a = '42';
$b = 42;
 
if( $a != $b ) {
   //这里始终执行不到
}

Comparison $a != $b returned FALSE but should return TRUE ! The string '42' is not equal to the integer 42

good:

Checking types and data using identity tests

$a = '42';
$b = 42;
 
if ($a !== $b) {
    // The expression is verified
}
The comparison $a !== $b returns TRUE.