PHP RegEx Example

Last modified on: October 19, 2024

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<h3>PHP Regular Expressions (RegEx)</h3>
<p>Regular expressions (RegEx) are powerful tools for pattern matching and manipulation in strings. PHP provides support for regular expressions through two main sets of functions: POSIX and Perl-Compatible Regular Expressions (PCRE). The latter is more commonly used due to its flexibility and extensive feature set.</p>
<hr />
<h4>Key Functions for Regular Expressions</h4>
<ol>
<li>
<p><strong>Basic Functions</strong>:</p>
<ul>
<li><strong><code>preg_match()</code></strong>: Searches for a pattern in a string and returns true or false.</li>
<li><strong><code>preg_match_all()</code></strong>: Searches for all matches of a pattern in a string.</li>
<li><strong><code>preg_replace()</code></strong>: Performs a search and replace on a string using a pattern.</li>
<li><strong><code>preg_split()</code></strong>: Splits a string by a regular expression.</li>
</ul>
</li>
<li>
<p><strong>Modifiers</strong>:</p>
<ul>
<li><strong><code>i</code></strong>: Case insensitive matching.</li>
<li><strong><code>m</code></strong>: Multiline matching.</li>
<li><strong><code>s</code></strong>: Allows <code>.</code> to match newline characters.</li>
</ul>
</li>
</ol>
<hr />
<h3>Example: Basic Usage of Regular Expressions</h3>
<h4>1. Using <code>preg_match()</code></h4>
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<pre class="language-php"><code>&lt;?php
$pattern = "/^Hello/";
$string = "Hello, World!";

if (preg_match($pattern, $string)) {
    echo "Pattern found at the beginning of the string.";
} else {
    echo "Pattern not found.";
}
?&gt;</code></pre>
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<h4>2. Using <code>preg_match_all()</code></h4>
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<pre class="language-php"><code>&lt;?php
$pattern = "/\d+/"; // Matches one or more digits
$string = "There are 12 apples and 34 oranges.";

preg_match_all($pattern, $string, $matches);

echo "Found numbers: " . implode(", ", $matches[0]); // Output: Found numbers: 12, 34
?&gt;</code></pre>
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<h4>3. Using <code>preg_replace()</code></h4>
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<pre class="language-php"><code>&lt;?php
$pattern = "/cat/i"; // Case insensitive
$replacement = "dog";
$string = "I have a Cat and a cat.";

$result = preg_replace($pattern, $replacement, $string);
echo $result; // Output: I have a dog and a dog.
?&gt;</code></pre>
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<h4>4. Using <code>preg_split()</code></h4>
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<pre class="language-php"><code>&lt;?php
$pattern = "/[\s,]+/"; // Split by spaces or commas
$string = "apple, orange, banana, grape";

$result = preg_split($pattern, $string);
print_r($result); // Output: Array ( [0] =&gt; apple [1] =&gt; orange [2] =&gt; banana [3] =&gt; grape )
?&gt;</code></pre>
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<hr />
<h3>Common Use Cases for Regular Expressions</h3>
<ol>
<li>
<p><strong>Email Validation</strong>:</p>
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<pre class="language-php"><code>&lt;?php
$email = "test@example.com";
$pattern = "/^[\w\.-]+@[\w\.-]+\.\w+$/";

if (preg_match($pattern, $email)) {
    echo "Valid email address.";
} else {
    echo "Invalid email address.";
}
?&gt;</code></pre>
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</li>
<li>
<p><strong>Phone Number Formatting</strong>:</p>
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<pre class="language-php"><code>&lt;?php
$phone = "123-456-7890";
$pattern = "/^(\d{3})-(\d{3})-(\d{4})$/";

if (preg_match($pattern, $phone, $matches)) {
    echo "Area code: " . $matches[1]; // Output: Area code: 123
} else {
    echo "Invalid phone number format.";
}
?&gt;</code></pre>
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</li>
</ol>
<hr />
<h3>Conclusion</h3>
<p>Regular expressions are a powerful tool in PHP for pattern matching, string manipulation, and data validation. By mastering the various functions and patterns available, you can efficiently handle complex string operations.</p>
<h3>&nbsp;</h3>
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