How do I check if a string contains a specific wor

Question

Consider:

$a = 'How are you?';

if ($a contains 'are')
    echo 'true';

Suppose I have the code above, what is the correct way to write the statement if ($a contains 'are')?

Answer 1

You can use the strstr function:

$haystack = "I know programming";
$needle   = "know";
$flag = strstr($haystack, $needle);

if ($flag){

    echo "true";
}

Without using an inbuilt function:

$haystack  = "hello world";
$needle = "llo";

$i = $j = 0;

while (isset($needle[$i])) {
    while (isset($haystack[$j]) && ($needle[$i] != $haystack[$j])) {
        $j++;
        $i = 0;
    }
    if (!isset($haystack[$j])) {
        break;
    }
    $i++;
    $j++;

}
if (!isset($needle[$i])) {
    echo "YES";
}
else{
    echo "NO ";
}

Answer 2

The strpos function works fine, but if you want to do case-insensitive checking for a word in a paragraph then you can make use of the stripos function of PHP.

For example,

$result = stripos("I love PHP, I love PHP too!", "php");
if ($result === false) {
    // Word does not exist
}
else {
    // Word exists
}

Find the position of the first occurrence of a case-insensitive substring in a string.

If the word doesn't exist in the string then it will return false else it will return the position of the word.

Answer 3

The function below also works and does not depend on any other function; it uses only native PHP string manipulation. Personally, I do not recommend this, but you can see how it works:

<?php

if (!function_exists('is_str_contain')) {
  function is_str_contain($string, $keyword)
  {
    if (empty($string) || empty($keyword)) return false;
    $keyword_first_char = $keyword[0];
    $keyword_length = strlen($keyword);
    $string_length = strlen($string);

    // case 1
    if ($string_length < $keyword_length) return false;

    // case 2
    if ($string_length == $keyword_length) {
      if ($string == $keyword) return true;
      else return false;
    }

    // case 3
    if ($keyword_length == 1) {
      for ($i = 0; $i < $string_length; $i++) {

        // Check if keyword's first char == string's first char
        if ($keyword_first_char == $string[$i]) {
          return true;
        }
      }
    }

    // case 4
    if ($keyword_length > 1) {
      for ($i = 0; $i < $string_length; $i++) {
        /*
        the remaining part of the string is equal or greater than the keyword
        */
        if (($string_length + 1 - $i) >= $keyword_length) {

          // Check if keyword's first char == string's first char
          if ($keyword_first_char == $string[$i]) {
            $match = 1;
            for ($j = 1; $j < $keyword_length; $j++) {
              if (($i + $j < $string_length) && $keyword[$j] == $string[$i + $j]) {
                $match++;
              }
              else {
                return false;
              }
            }

            if ($match == $keyword_length) {
              return true;
            }

            // end if first match found
          }

          // end if remaining part
        }
        else {
          return false;
        }

        // end for loop
      }

      // end case4
    }

    return false;
  }
}

Test:

var_dump(is_str_contain("test", "t")); //true
var_dump(is_str_contain("test", "")); //false
var_dump(is_str_contain("test", "test")); //true
var_dump(is_str_contain("test", "testa")); //flase
var_dump(is_str_contain("a----z", "a")); //true
var_dump(is_str_contain("a----z", "z")); //true 
var_dump(is_str_contain("mystringss", "strings")); //true 

Answer 4

Look at strpos():

<?php
    $mystring = 'abc';
    $findme   = 'a';
    $pos = strpos($mystring, $findme);

    // Note our use of ===. Simply, == would not work as expected
    // because the position of 'a' was the 0th (first) character.
    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 5

Here is a little utility function that is useful in situations like this

// returns true if $needle is a substring of $haystack
function contains($needle, $haystack)
{
    return strpos($haystack, $needle) !== false;
}

Answer 6

I'm a bit impressed that none of the answers here that used strpos, strstr and similar functions mentioned Multibyte String Functions yet (2015-05-08).

Basically, if you're having trouble finding words with characters specific to some languages, such as German, French, Portuguese, Spanish, etc. (e.g.: ä, é, ô, ç, º, ñ), you may want to precede the functions with mb_. Therefore, the accepted answer would use mb_strpos or mb_stripos (for case-insensitive matching) instead:

if (mb_strpos($a,'are') !== false) {
    echo 'true';
}

If you cannot guarantee that all your data is 100% in UTF-8, you may want to use the mb_ functions.

A good article to understand why is The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) by Joel Spolsky.