String Length

To find out how long a string is, use strlen().

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<?php
$password = "secret123";

echo strlen($password);

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9

Spaces and punctuation count too.

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<?php
echo strlen("Hello, world!");

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13

Use it to validate input

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<?php
$username = "al";

if (strlen($username) < 3) {
    echo "Username must be at least 3 characters.";
}

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Username must be at least 3 characters.

strlen counts bytes

strlen() counts bytes, not characters. For English letters, they are the same. For characters outside basic English, they are not.

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<?php
echo strlen("naive") . "\n";
echo strlen("naïve") . "\n";
echo mb_strlen("naïve");

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mb_strlen() counts real characters. Use it whenever the text could contain accents, Hindi, emoji or other non-English characters. See Multibyte Strings.

Count words

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<?php
$text = "PHP is easy to learn";

echo str_word_count($text);

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str_word_count() is fine for English text. For other languages, split the text yourself.

Empty strings

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<?php
var_dump(strlen("") === 0);
var_dump("" === "");

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bool(true)
bool(true)

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<?php
$text = "Learning PHP step by step";
$limit = 100;

echo "Characters left: " . ($limit - mb_strlen($text));

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Characters left: 75