Check if string contains specific words?

This means the string has to be resolved into words (see note below).

One way to do this and to specify the separators is using preg_split:

<?php

function contains_word($str, $word) {
  // split string into words
  // separators are substrings of at least one non-word character
  $arr = preg_split('/\W+/', $str, NULL, PREG_SPLIT_NO_EMPTY);
  
  // now the words can be examined each
  foreach ($arr as $value) {
    if ($value === $word) {
      return true;
    }
  }
  return false;
}

function test($str, $word) {
  if (contains_word($str, $word)) {
    echo "string '" . $str . "' contains word '" . $word . "'\n";
  } else {
    echo "string '" . $str . "' does not contain word '" . $word . "'\n" ;
  }
}

$a = 'How are you?';

test($a, 'are');
test($a, 'ar');
test($a, 'hare');

?>

A run gives

$ php -f test.php                   
string 'How are you?' contains word 'are' 
string 'How are you?' does not contain word 'ar'
string 'How are you?' does not contain word 'hare'

Note: Here we do not mean word for every sequence of symbols.

A practical definition of word is in the sense the PCRE regular expression engine, where words are substrings consisting of word characters only, being separated by non-word characters.

A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl " word ". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place (..)

Check if string contains specific words?

This means the string has to be resolved into words (see note below).

One way to do this and to specify the separators is using preg_split (doc):

<?php

function contains_word($str, $word) {
  // split string into words
  // separators are substrings of at least one non-word character
  $arr = preg_split('/\W+/', $str, NULL, PREG_SPLIT_NO_EMPTY);
  
  // now the words can be examined each
  foreach ($arr as $value) {
    if ($value === $word) {
      return true;
    }
  }
  return false;
}

function test($str, $word) {
  if (contains_word($str, $word)) {
    echo "string '" . $str . "' contains word '" . $word . "'\n";
  } else {
    echo "string '" . $str . "' does not contain word '" . $word . "'\n" ;
  }
}

$a = 'How are you?';

test($a, 'are');
test($a, 'ar');
test($a, 'hare');

?>

A run gives

$ php -f test.php                   
string 'How are you?' contains word 'are' 
string 'How are you?' does not contain word 'ar'
string 'How are you?' does not contain word 'hare'

Note: Here we do not mean word for every sequence of symbols.

A practical definition of word is in the sense the PCRE regular expression engine, where words are substrings consisting of word characters only, being separated by non-word characters.

A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl " word ". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place (..)

Check if string contains specific words?

This means the string has to be resolved into words (see note below).

One way to do this and to specify the separators is using preg_split:

<?php
$a = 'How are you?';

$arr = preg_split('/\b/', $a);

foreach ($arr as $word) {
  if ($word === 'are') {
    echo 'true';
  }
  break;  // stop traversing the list of words
}
?>

Note: Here we do not mean word for every sequence of symbols.

A practical definition of word is in the sense the PCRE regular expression engine, where words are substrings consisting of word characters only, being separated by non-word characters.

A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl " word ". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place (..)

Check if string contains specific words?

This means the string has to be resolved into words (see note below).

One way to do this and to specify the separators is using preg_split:

<?php

function contains_word($str, $word) {
  // split string into words
  // separators are substrings of at least one non-word character
  $arr = preg_split('/\W+/', $str, NULL, PREG_SPLIT_NO_EMPTY);
  
  // now the words can be examined each
  foreach ($arr as $value) {
    if ($value === $word) {
      return true;
    }
  }
  return false;
}

function test($str, $word) {
  if (contains_word($str, $word)) {
    echo "string '" . $str . "' contains word '" . $word . "'\n";
  } else {
    echo "string '" . $str . "' does not contain word '" . $word . "'\n" ;
  }
} 

$a = 'How are you?';

test($a, 'are');
test($a, 'ar');
test($a, 'hare');

?>

A run gives

$ php -f test.php                   
string 'How are you?' contains word 'are' 
string 'How are you?' does not contain word 'ar'
string 'How are you?' does not contain word 'hare'

Note: Here we do not mean word for every sequence of symbols.

A practical definition of word is in the sense the PCRE regular expression engine, where words are substrings consisting of word characters only, being separated by non-word characters.

A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl " word ". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place (..)