Using byte based comparison for startsWith and endsWith since mb_str functions are slow and it doesn't matter what the encoding is in this instance. another performance hit is the current use of mb_strpos since the full length of the string will be checked, resulting in increasingly slow performance as the str length increases.

test-str.php

<?php
$testHaystack = trim(file_get_contents( 'data-large.txt' )); //~4.5MB of text
//$testHaystack = trim(file_get_contents( 'data-small.txt')); //~1KB of text
//$testHaystack = 'السلام علیکم ورحمة الله وبرکاتهöLorem ipsum dolor sit amet voluptatem?öالسلام علیکم ورحمة الله وبرکاته';//Short string test

$validMatch         = "السلام علیکم ورحمة الله وبرکاتهöLorem";
$invalidMatch       = "I'm not anywhere in there";
$numberOfIterations = 10000;

//------------------[ startsWith valid ]------------------//
sleep( 1 );

echo "startsWith against validMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( startsWith( $testHaystack, $validMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ startsWith invalid ]------------------//
sleep( 1 );

echo "startsWith against invalidMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( startsWith( $testHaystack, $invalidMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ startsWithAlt valid ]------------------//
sleep( 1 );

echo "startsWithAlt against validMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( startsWithAlt( $testHaystack, $validMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ startsWithAlt invalid ]------------------//
sleep( 1 );

echo "startsWithAlt against invalidMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( startsWithAlt( $testHaystack, $invalidMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

/*********************************************************
 * Ends with
 ********************************************************/

$validMatch   = "voluptatem?öالسلام علیکم ورحمة الله وبرکاته";
$invalidMatch = "I'm not anywhere in there";
//------------------[ endsWith valid ]------------------//
sleep( 1 );

echo "endsWith against validMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( endsWith( $testHaystack, $validMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ endsWith invalid ]------------------//
sleep( 1 );

echo "endsWith against invalidMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( endsWith( $testHaystack, $invalidMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ endsWithAlt valid ]------------------//
sleep( 1 );

echo "endsWithAlt against validMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( endsWithAlt( $testHaystack, $validMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ endsWithAlt invalid ]------------------//
sleep( 1 );

echo "endsWithAlt against invalidMatch\n";
$startTime1 = microtime( true );
$matches    = 0;
for ( $i = 0; $i < $numberOfIterations; $i ++ ) {
	if ( endsWithAlt( $testHaystack, $invalidMatch ) ) {
		$matches ++;
	}
}
echo "Finished in ", microtime( true ) - $startTime1, " seconds, {$matches} matches found\n\n";

//------------------[ functions to test ]------------------//
/**
 * @param $haystack
 * @param $needles
 *
 * @return bool
 */
function startsWith( $haystack, $needles ) {
	foreach ( (array) $needles as $needle ) {
		if ( $needle != '' && mb_strpos( $haystack, $needle ) === 0 ) {
			return true;
		}
	}

	return false;
}

/**
 * @param $haystack
 * @param $needles
 *
 * @return bool
 */
function startsWithAlt( $haystack, $needles ) {
	foreach ( (array) $needles as $needle ) {
		//byte based comparison since we don't need to deal with the values after comparison
		if ( $needle != '' && substr( $haystack, 0, strlen( $needle ) ) === $needle ) {
			return true;
		}
	}

	return false;
}

/**
 * @param $haystack
 * @param $needles
 *
 * @return bool
 */
function endsWith( $haystack, $needles ) {
	foreach ( (array) $needles as $needle ) {

		if ( (string) $needle === mb_substr( $haystack, -mb_strlen( $needle ), null, 'UTF-8' ) ) {
			return true;
		}
	}

	return false;
}

/**
 * @param $haystack
 * @param $needles
 *
 * @return bool
 */
function endsWithAlt( $haystack, $needles ) {
	foreach ( (array) $needles as $needle ) {
		//byte based comparison since we don't need to deal with the values after comparison
		if ( (string) $needle === substr( $haystack, -strlen( $needle ) ) ) {
			return true;
		}
	}

	return false;
}