Create an alphanumeric captcha with different text -and linecolours

createCaptcha.php

<?php

/* Create an alphanumeric captcha the easy way - by ToshY | 05-05-2019 */

function imageCaptcha($chars = 6, $lines, $bg_colour = array('R'=>204,'G'=>153,'B'=>255), $line_colours = array(array('R'=>153,'G'=>51,'B'=>102)), $txt_colours = array(array('R'=>0,'G'=>0,'B'=>0),array('R'=>255,'G'=>255,'B'=>255)), $fonts = array('arial.ttf')){
	// dimensions / fontsize based on amount of characters
	$MW = round($chars * ( 100 / 3) ); $MH = round($MW / 3); $fs = round( ( 30 * (1 - exp( -0.005 * $MW ) ) ) , 2);

	// init image with user dimensions
	$img = imagecreatetruecolor( $MW, $MH );

	// set bg
	$bg = call_user_func_array('imagecolorallocate', array_merge( array($img), $bg_colour ) );
	imagefill( $img, 0, 0, $bg );

	// line colours array
	$lineclrs = array(); $cl = count($line_colours);
	for($i = 0; $i < $cl; $i++){
		$lineclrs[] = call_user_func_array('imagecolorallocate', array_merge( array($img), $line_colours[$i] ) );
	}

	// add lines to img
	for($j = 0; $j < $lines; $j++) {
		imagesetthickness( $img, rand( 1, floor($fs / 5) ) );
		imageline( $img, rand( 0, $MW ), 0, rand( 0, $MW ), $MH, $lineclrs[array_rand($lineclrs)] );
	}

	// text colours array
	$txtclrs = array(); $ct = count($txt_colours);
	for($k = 0; $k < $ct; $k++){
		$txtclrs[] = call_user_func_array('imagecolorallocate', array_merge( array($img), $txt_colours[$k] ) );
	}

	// get random letter and add to img
	$strcapt = '';
	for($l = 0, $x = 8; $l < $chars; $l++, $x += round((( $MW - ( 1.5 * $fs ) ) / ($chars - 1)))){
		// get random letter
		$strcapt .= ($rstr = gRS(1,'101'));
		// add letter to image
		imagettftext($img, $fs, rand(-33,33), $x, rand( $fs + 5, $MH - 5), $txtclrs[array_rand($txtclrs)], $fonts[array_rand($fonts)], $rstr);
	}

	// add to session
	$_SESSION['img_captcha'] = $strcapt;

	// display img
	header('Content-type: image/png');
	imagepng($img);
	imagedestroy($img);
}

function gRS($length, $opt = '111') {
	$r = '';
	//numbers only
	$r .= ( ( (int) $opt[0] === 1) ? '012345678923456789' : '');
	//numbers with small letters
	$r .= ( ( (int) $opt[1] === 1) ? 'abcdefghijklmnopqrstuvwxyz' : '');
	//numbers with small and capital letters
	$r .= ( ( (int) $opt[2] === 1) ? 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' : '');

	return ( ($r) ? substr( str_shuffle( str_repeat( $r, ceil( $length / strlen( $r ) ) ) ), 1, $length) : NULL);
}

echo '<img src="'.imageCaptcha(50, 20, array(50,100,200), array(array(100,20,50),array(10,50,200),array(70,10,50)), array(array(66, 244, 158), array(247, 89, 49), array(255, 255, 255), array(0, 0 ,0)), array('/path/to/a/font.ttf','/path/to/another/font.ttf')).'">';
?>