I have to check if an asterisk exists in the string, but it always shows that there is no asterisk.
Why does strpos() not work? I have also tried stripos(), mb_strpos(), and mb_stripos() without luck. 
<?php
$str = "****123";
if(strpos($str, '*') == false){
    echo 'There is no asterisk in the string';  
} else {
    echo 'There is asterisk in the string';     
}
There is no asterisk in the string.
strpos() returns an integer (0 or more) or FALSE if not found. In PHP, the comparison with 0 and FALSE are different only if you use a strict equality (===):
$str = "****123";
if(strpos($str, '*') === false){
    echo 'There is no asterisk in the string';  
} else {
    echo 'There is asterisk in the string';     
}
Outputs:
There is asterisk in the string
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