How to process text using string functions in PHP? 1. Use strlen() to get the string length, for example, strlen("Hello") returns 5, which is suitable for verifying the input length, but note that multi-byte characters need to use mb_strlen(). 2. Use strpos() to find the location of the substring, such as strpos("The quick brown fox", "brown") to return 10, which is often used to check the mailbox or URL format. Note that using === false to determine that it is not found, and you can use strpos() to perform case-insensitive searches. 3. Use substr() to extract some strings, such as substr("Programming", 0, 3) to output "Pro", which supports negative counting from the end, which is commonly used to intercept titles, file extensions, or hide sensitive information. 4. Use str_replace() to replace text, such as str_replace("JavaScript", "PHP", ...) to replace JavaScript with PHP, supports batch replacement of swear words in arrays, pay attention to case sensitivity and optionally use preg_replace() for regular replacement. These functions are suitable for common text manipulation tasks.

When you're working with text in PHP, string functions are essential tools for manipulating and analyzing strings. Functions like strlen() , strpos() , substr() , and str_replace() let you do everything from checking length to searching, slicing, and replacing parts of a string.

How to get the length of a string with strlen()

If you want to know how many characters are in a string — spaces and punctuation included — strlen() is your go-to function. It returns the number of characters in the string as an integer.

For example:

 $text = "Hello";
echo strlen($text); // Outputs: 5

This can be handy when validating user input, like making sure a password is long enough or checking if a comment isn't too long.

A quick note: strlen() counts bytes, not actual characters in some multibyte cases (like emoji or certain non-English letters). If you're dealing with UTF-8 or other encodings, consider using mb_strlen() instead.

Finding where something appears with strpos()

The strpos() function helps you locate the position of one string inside another. It returns the index (starting from 0) where the substring first appears. If it doesn't find anything, it returns false .

Example:

 $text = "The quick brown fox";
echo strpos($text, "brown"); // Outputs: 10

A common use case might be checking if an email contains "@" or ensuring that a URL starts with "http://".

Some gotchas:

• Since it returns 0 when found at the beginning, always use === false to check if it's not found.
• It's case-sensitive by default. Use stripos() if you want a case-insensitive search.

Extracting part of a string with substr()

Sometimes you just need a slice of a string — maybe the first few characters of a title or trimming off extra characters. That's what substr() does.

Basic usage:

 $text = "Programming";
echo substr($text, 0, 3); // Outputs: Pro

You can also use negative numbers to count from the end:

 echo substr($text, -3); // Outputs: ing

Common scenarios include shortening long titles for display, grabbing file extensions, or masking sensitive data like showing only the last four digits of a phone number.

Replacing parts of a string with str_replace()

Need to swap out one bit of text for another? str_replace() handles that. It searches for a value and replaces it with something else.

Example:

 $text = "I love JavaScript!";
echo str_replace("JavaScript", "PHP", $text); // Outputs: I love PHP!

It works with arrays too, which makes it easy to replace multiple values ??at once:

 $badWords = ["bad", "ugly"];
echo str_replace($badWords, "***", "This is bad and ugly."); 
// Outputs: This is *** and ***.

Just keep in mind:

• It's case-sensitive by default.
• If you need more complex pattern matching, look into preg_replace() for regular expressions.

These basic string functions cover a lot of ground. They're fast, built-in, and usually the most straightforward way to handle everyday text manipulation in PHP. Once you get comfortable with them, combining them becomes second nature — like pulling the domain from an email address or cleaning up messy user input before saving it.

Basically that's it.

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