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PHP str_starts_with() Function

Quick summary: The PHP str_starts_with() function checks if a string starts with a given substring.

PHP str_starts_with() Syntax 

str_starts_with(string $haystack, string $needle): bool
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PHP str_starts_with() Basic examples 

var_dump(str_starts_with("Hello world", "Hello"));
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Output:
bool(true)

Returns true if the string starts with the given substring.

var_dump(str_starts_with("Hello world", "world"));
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Output:
bool(false)

Returns false if the substring is not at the start.

PHP str_starts_with() Real-world usage 

$path = "/api/users";
if (str_starts_with($path, "/api")) {
    echo "API route";
}
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Output:
API route

Detects URL prefixes.

PHP str_starts_with() Edge cases 

var_dump(str_starts_with("test", ""));
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Output:
bool(true)

An empty string is always a valid prefix.

PHP str_starts_with() Common mistakes

Reimplementing prefix checks manually

Using substr or strpos is unnecessary.

Incorrect
substr("test", 0, 2) === "te";
Correct
str_starts_with("test", "te");

Use str_starts_with() for clarity and safety.

PHP str_starts_with() Frequently Asked Questions

What does str_starts_with() do in PHP?

str_starts_with() checks if a string starts with a given substring and returns true or false.

Is str_starts_with() case-sensitive?

Yes, str_starts_with() is case-sensitive.

What does str_starts_with() return?

It returns true if the string starts with the given substring, otherwise false.

Can str_starts_with() return 0?

No, it always returns a boolean value.

Is str_starts_with() available in all PHP versions?

No, it was introduced in PHP 8.0.

How to replicate str_starts_with() in older PHP?

Use strncmp($string, $search, strlen($search)) === 0.

Does str_starts_with() support empty strings?

Yes, every string starts with an empty string, so it returns true.

Does str_starts_with() modify the string?

No, it only checks the condition and does not modify the string.

Is str_starts_with() multibyte-safe?

It operates on bytes and may not fully support multibyte encodings.

What is the difference between str_starts_with() and strpos()?

str_starts_with() returns a boolean, while strpos() returns position or false.

What is a real-world use case of str_starts_with()?

It is commonly used to validate prefixes such as URLs, file paths, or tokens.

Can str_starts_with() be used for validation?

Yes, it is often used to validate input patterns or prefixes.

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