如何在字符串中获取完整的子字符串？

Question

I have variable $mystring = "abc+adb" and I am trying to find ab in the $mystring. I want to throw a message which say ab does not exist in $mystring, but the following code keeps picking ab from abc, I want ab to be treated as a standalone substring;

$mystring = 'abc+adb';
$findme   = 'bc';
$pos = strpos($mystring, $findme);
if ($pos === false) {
    echo "The string '$findme' was not found in the string '$mystring'";
} 
else {
    echo "The string '$findme' was found in the string '$mystring'";
    echo " and exists at position $pos";
}

Answer 1

You shouldn't use strpos for that.

strpos - Find the position of the first occurrence of a substring in a string

You can use a regular expression to do that. By no means am I a master of regular expression, but a simple example that meets your immediate need is:

preg_match('/\bab\b/', $mystring);

The preg_match function will return 1 if successful, 0 if no matches found or false in if there was an error.

$mystring = 'abc+adb';
$findme   = 'bc';
if ( preg_match('/\b'  . $findme . '\b/',$mystring) ) {
    echo "The string '$findme' was not found in the string '$mystring'";
} else {
    $pos = strpos($mystring, $findme);
    echo "The string '$findme' was found in the string '$mystring'";
    echo " and exists at position $pos";
}