why i get true from in_array("a",$array_name)

Question

$array_name=array(1,2,3,4,5,6,7,8,9,0);
var_dump(in_array("a",$array_name));

why I get true?

but i will get false from

var_dump(in_array("a",$array_name,true));

Answer 1

With your exact posted code, you cannot possibly be getting true:

php > var_dump(in_array("a", array(1,2,3,4,5,6,7,8)));
bool(false)

But if you had a false-y value in the array:

php > var_dump(in_array("a", array(0,1,2,3,4,5,6,7,8)));
                                   ^----- false-y value
bool(true)
php > var_dump(in_array("a", array(0,1,2,3,4,5,6,7,8), true));
bool(false)

Then you would get your expected results. Passing the 3rd true argument to in_array forces a strict equality test internally, e.g. === instead of ==:

php > var_dump("a" == 0, "a" === 0);
bool(true)
bool(false)

Answer 2

Firstly you have different arguments in in_array() function.

in first call you have strict = false by default in second it's true

This does not means you should get true because false is proper returned value

Edit:

I thought about code you give in comment and I assume "aaa" is casted to integer 0 then 0 is found in array so it returns true;

Try to remove 0 from your array and it will return false.

in_array() has pretty unexpected behavior that is why it is good to use strict option set to true.

<?php

 $array = array(1,2,3,4,5,6,7,8,9,0); 
 $array2 = array(1,2,3,4,5,6,7,8,9); 
 var_dump(in_array("aaa", $array, false));
 var_dump(in_array("aaa", $array2, false));

?>

Output:

bool(true) bool(false)