为什么in_array（）在这种情况下不起作用？ （来自file（）的数组）

Why is this code not working?

I have test.txt it contains:

A
B
C

My PHP code is:

$arr = file('test.txt');

if (in_array('A', $arr)) {
   echo 'A is found';
}

Result. nothing. But this following code works fine:

if (in_array('C', $arr)) {
    echo 'C is found';
}

Can someone help me?

Because file() will not remove the newline symbols from the end of each line, if you don't tell him to do so

$arr = file('test.txt', FILE_IGNORE_NEW_LINES);

or remove it yourself, what will remove any other whitespace from the beginning and end of each line

$array = array_map('trim', file('test.txt'));