Want to Check If a String Starts with a Certain Character? Try PHP’s substr Function!

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Title: Want to Check If a String Starts with a Certain Character? Try PHP’s substr Function!</p>
<p>During development, it’s common to need to determine whether a string starts with a specific character or substring. PHP offers several ways to achieve this, and using the substr function is a simple and efficient solution.</p>
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<p>Introduction to the substr Function<br>
The substr() function is used to return part of a string. Its basic usage is:<br>
string substr ( string $string , int $start [, int $length ] )</p>
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<p>$string: The input string.</p>
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<p>$start: The starting position (beginning from 0).</p>
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<p>$length: Optional, the length of the returned substring.</p>
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<p>Using substr to Check String Prefix</p>
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<p>Suppose we want to check whether a string $str starts with a substring $prefix. We can use substr to extract the beginning of the string and compare it with $prefix:</p>
<p>Here’s an example:<br>
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<p>function startsWith($str, $prefix) {<br>
// Get the length of $prefix<br>
$len = strlen($prefix);<br>
// Extract the first $len characters of the string<br>
$start = substr($str, 0, $len);<br>
// Check if they are equal<br>
return $start === $prefix;<br>
}</p>
<p>// Test examples<br>
$str = "Hello, world!";<br>
$prefix1 = "Hello";<br>
$prefix2 = "world";</p>
<p>echo startsWith($str, $prefix1) ? "'$str' starts with '$prefix1'\n" : "'$str' does not start with '$prefix1'\n";<br>
echo startsWith($str, $prefix2) ? "'$str' starts with '$prefix2'\n" : "'$str' does not start with '$prefix2'\n";</p>
<p>/*<br>
Output:<br>
'Hello, world!' starts with 'Hello'<br>
'Hello, world!' does not start with 'world'</p>
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<p>Notes</p>
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<p>When using substr with Chinese strings, incomplete character cuts may occur since each Chinese character occupies multiple bytes. For handling Chinese strings, it’s better to use mb_substr.</p>
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<p>If you need case-insensitive checking, convert both the string and the prefix to the same case (e.g., strtolower).</p>
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<p>Conclusion<br>
Using the substr function to check if a string starts with a particular character or substring is concise and easy to understand. It’s a common solution among PHP developers. Of course, depending on your requirements and character encoding, you might also consider alternatives such as strpos or mb_substr.</p>
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<p data-is-last-node="" data-is-only-node="">Hopefully, this article helps you better understand and apply PHP’s substr function!<br>
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