Word matching in php

PHP Regular Expressions

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

A regular expression can be a single character, or a more complicated pattern.

Regular expressions can be used to perform all types of text search and text replace operations.

Syntax

In PHP, regular expressions are strings composed of delimiters, a pattern and optional modifiers.

In the example above, / is the delimiter, w3schools is the pattern that is being searched for, and i is a modifier that makes the search case-insensitive.

The delimiter can be any character that is not a letter, number, backslash or space. The most common delimiter is the forward slash (/), but when your pattern contains forward slashes it is convenient to choose other delimiters such as # or ~.

Regular Expression Functions

PHP provides a variety of functions that allow you to use regular expressions. The preg_match() , preg_match_all() and preg_replace() functions are some of the most commonly used ones:

Function	Description
preg_match()	Returns 1 if the pattern was found in the string and 0 if not
preg_match_all()	Returns the number of times the pattern was found in the string, which may also be 0
preg_replace()	Returns a new string where matched patterns have been replaced with another string

Using preg_match()

The preg_match() function will tell you whether a string contains matches of a pattern.

Example

Use a regular expression to do a case-insensitive search for «w3schools» in a string:

Using preg_match_all()

The preg_match_all() function will tell you how many matches were found for a pattern in a string.

Example

Use a regular expression to do a case-insensitive count of the number of occurrences of «ain» in a string:

$str = «The rain in SPAIN falls mainly on the plains.»;
$pattern = «/ain/i»;
echo preg_match_all($pattern, $str); // Outputs 4
?>

Using preg_replace()

The preg_replace() function will replace all of the matches of the pattern in a string with another string.

Example

Use a case-insensitive regular expression to replace Microsoft with W3Schools in a string:

$str = «Visit Microsoft!»;
$pattern = «/microsoft/i»;
echo preg_replace($pattern, «W3Schools», $str); // Outputs «Visit W3Schools!»
?>

Regular Expression Modifiers

Modifiers can change how a search is performed.

Modifier	Description
i	Performs a case-insensitive search
m	Performs a multiline search (patterns that search for the beginning or end of a string will match the beginning or end of each line)
u	Enables correct matching of UTF-8 encoded patterns

Regular Expression Patterns

Brackets are used to find a range of characters:

Expression	Description
[abc]	Find one character from the options between the brackets
[^abc]	Find any character NOT between the brackets
4	Find one character from the range 0 to 9

Metacharacters

Metacharacters are characters with a special meaning:

Metacharacter	Description
|	Find a match for any one of the patterns separated by | as in: cat|dog|fish
.	Find just one instance of any character
^	Finds a match as the beginning of a string as in: ^Hello
$	Finds a match at the end of the string as in: World$
\d	Find a digit
\s	Find a whitespace character
\b	Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b
\uxxxx	Find the Unicode character specified by the hexadecimal number xxxx

Quantifiers

Quantifiers define quantities:

Quantifier	Description
n+	Matches any string that contains at least one n
n*	Matches any string that contains zero or more occurrences of n
n?	Matches any string that contains zero or one occurrences of n
n	Matches any string that contains a sequence of X n‘s
n	Matches any string that contains a sequence of X to Y n‘s
n	Matches any string that contains a sequence of at least X n‘s

Note: If your expression needs to search for one of the special characters you can use a backslash ( \ ) to escape them. For example, to search for one or more question marks you can use the following expression: $pattern = ‘/\?+/’;

Grouping

You can use parentheses ( ) to apply quantifiers to entire patterns. They also can be used to select parts of the pattern to be used as a match.

Example

Use grouping to search for the word «banana» by looking for ba followed by two instances of na:

Complete RegExp Reference

The reference contains descriptions and examples of all Regular Expression functions.

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String contains multiple words

There are several ways to determine if a given string contains a specific word in PHP. It depends on the program context we are solving.

As we are here to check that a PHP string contains multiple words, therefore, assuming that you are already aware of a single word search within the string. Therefore first we will see how to check if a string contains any word in short.

One of the best ways to check single word using PHP function strpos

$searchText = «QuizCure»; $givenString = «Programming articles listed on QuizCure belongs to java, python, PHP and more»; if(strpos($givenString, $searchText) !== false) < echo "QuizCure text Found!"; >else

Result: QuizCure text Found!

Explanation:

• strpos is used to check the position of the first existence of a search word
• strpos is case-sensitive. Therefore it will match the same case letters only.
• In our example above we have searchText as QuizCure and the given string also contains the same set of upper and lowercase combinations of word QuizCure.
• strpos($givenString, $searchText) return false if it doesn’t find the searchText position in the given string. Therefore I used criteria strpos($givenString, $searchText) !== false to test.

Now let’s explore how can we check string containing more than one word in a given string in the following ways

Scroll for More Useful Information and Relevant FAQs

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Check If A String Contains A Specific Word In PHP

Often, developers want to check string contains a specific word or not in PHP. For that, we can use strpos() and preg_match() functions to do that. Let’s see how to do it.

Check If a String Contains a Specific Word

01 Find Exact Match Using the PHP preg_match() Function

You can use the PHP preg_match() function to check whether a text contains a specific word or not.

Use: The preg_match() function is used to find the exact match of a pattern in a string of text using a regular expression search.

Return: This function will return true if the pattern is matched otherwise it will return false .

The following example will check for the exact match of the word like we are searching for aware then it will only search for the aware word and not a partial word like «beware», «unaware», «awareness», etc.

The \b expression in the pattern specify a word boundary.

Case Insensitive Search with preg_match()

For case-insensitive search put the «i» after the pattern delimiter as shown below:

In the above example, we are checking for aware specific word but our string contains a capital AWARE but although it will return A match was found . due to case-insensitive searches.

02 Use the PHP strpos() Function

You can also use the PHP’s strpos() function to check whether a string contains a specific word or not.

The strpos() function will return the position of the first occurrence of a substring in a string. It will return false if the match not found.

Please note that strpos() start searching from 0 index so use strict comparision operator using === or !== otherwise it will considered 0 = false .

Let’s see the example for better understanding:

You can also check if the string contains a word or not by using other PHP functions like stripos(), strstr(), stristr(), substr_count(), mb_strpos(), etc.

Why to Use preg_match() And Not strpos()

The preg_match() is better for word matching in comparison to strpos() because if you are checking the string contains a word like «are» and if your string contains words like careful, beware, prepare, etc. then strpos() will also return true.

To understand this situation please considered the below example:

The above example should return the false , but it’s returning true as output.

That’s it for now. We hope this article helped you to check if a string contains a specific word in PHP.

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