Replace String Prefixes with Laravel's replaceStart Method

Need to replace text at the beginning of a string? Laravel's Str::replaceStart method offers a precise way to modify strings only when they start with specific content.

Basic Usage

Replace text at the start of a string:

use Illuminate\Support\Str;

// Successful replacement
$replaced = Str::replaceStart('Hello', 'Laravel', 'Hello World');
// Result: 'Laravel World'

// No replacement (doesn't start with 'World')
$replaced = Str::replaceStart('World', 'Laravel', 'Hello World');
// Result: 'Hello World'

Real-World Example

Here's how you might use it in a URL formatter:

class UrlFormatter
{
    public function normalizeProtocol(string $url, string $protocol = 'https')
    {
        // Replace http:// with https://
        $url = Str::replaceStart('http://', $protocol . '://', $url);
        
        // Add protocol if missing
        if (!str_starts_with($url, $protocol . '://')) {
            $url = $protocol . '://' . $url;
        }
        
        return $url;
    }

    public function standardizeDomain(string $url, string $mainDomain)
    {
        // Replace www with main domain
        $url = Str::replaceStart('www.', $mainDomain . '.', $url);
        
        // Replace dev with main domain
        $url = Str::replaceStart('dev.', $mainDomain . '.', $url);
        
        return $url;
    }

    public function cleanupApiEndpoint(string $endpoint)
    {
        // Remove leading /api if present
        return Str::replaceStart('/api', '', $endpoint);
    }
}

// Usage
$formatter = new UrlFormatter();

echo $formatter->normalizeProtocol('http://example.com');
// Output: 'https://example.com'

echo $formatter->standardizeDomain('www.example.com', 'app');
// Output: 'app.example.com'

echo $formatter->cleanupApiEndpoint('/api/users');
// Output: '/users'

The replaceStart method provides precise control over string modifications when you need to target content at the beginning of a string.

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