PHP string == comparison operator side effects_PHP tutorial

Copy code The code is as follows:

$a = '212345678912000005';
$b = '212345678912000001';
var_dump ($a == $b);

The output of this code is bool(true), which means that this judgment will conclude that the two are equal. Similar characteristics are in the in_array() function When the three parameters are false or not set. The reason is to first determine whether the string is a number, then convert it to long or double (C language data type) and then determine - use zendi_smart_strcmp. However, the comments in the source code say that the statement considers overflow In the case of {
/* Both values ​​overflowed and have the same sign,

* so a numeric comparison would be inaccurate */ goto string_cmp; }

dval1 and dval2 They are the values ​​after converting the two strings into double types. But why is this still the case? Maybe this judgment is not correct. Let’s study further...

Solution, use three equal signs "== ="Instead of two equal signs "==", the in_array() function sets the third parameter to true: in_array('val', $array, true).



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TechArticleCopy the code as follows: $a = '212345678912000005'; $b = '212345678912000001'; var_dump($a = = $b); The output of this code is bool(true), which means that this judgment will lead to the conclusion that the two are consistent...