Questions about In_array of digital array

On the problem of digital array In_array

Among PHP
$a array contains numbers from 1 to 100

if (In_array (1, $a) {
..........
}

This will put 11, 21. Wait, the 1 of the judges come in.

This is still not working.
In_array (1, $a, TRUE)

How to separate the 1 and 11 in the in array
------to solve the idea----------------------
What's wrong with it?
if (In_array ( 1, Array ( 1, 11,21,31))) {
Echo ' in ';
}
1 in the array, so the output

Reverse to write this
If !In_array (1, Array (11,21,31))) {
echo ' not ';
}

------to solve the idea----------------------
if (In_array (1, $a) {
..........
}

This will put 11, 21. And so on, 1 of all judgment came in.
It's not going to happen.

 
  $a = array (11,12);
Var_dump (In_array (1, $a)); False
?>

Boolean false

 
  $a = array (for each);
Var_dump (In_array (1, $a)); True
?>

Boolean true

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