JAVASCRIPT

str_contains — Determine if a string contains a given substring

<?php
if (str_contains('abc', '')) {
    echo "Checking the existence of the empty string will always return true";
}
?>

How to check if the text of a string includes the "str" you are looking for

//Here are the commonly used JavaScript String methods:

var abc = "abcdefghijklmnopqrstuvwxyz";
var esc = 'I don't 
 know';   // 
 new line
var len = abc.length;           // string length
abc.indexOf("lmno");            // find substring, -1 if doesn't contain 
abc.lastIndexOf("lmno");        // last occurance
abc.slice(3, 6);                // cuts out "def", negative values count from behind
abc.replace("abc","123");       // find and replace, takes regular expressions
abc.toUpperCase();              // convert to upper case
abc.toLowerCase();              // convert to lower case
abc.concat(" ", str2);          // abc + " " + str2
abc.charAt(2);                  // character at index: "c"
abc[2];                         // unsafe, abc[2] = "C" doesn't work
abc.charCodeAt(2);              // character code at index: "c" -> 99
abc.split(",");                 // splitting a string on commas gives an array
abc.split("");                  // splitting on characters
128.toString(16);               // number to hex(16), octal (8) or binary (2)