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<?php
// Paste this function in your theme's function.php file

function greeklish_permalinks_sanitize_title($text) {
	if ( !is_admin() ) return $text;

	$expressions = array(
		'/[αΑ][ιίΙΊ]/u' => 'e',
		'/[οΟΕε][ιίΙΊ]/u' => 'i',
		'/[αΑ][υύΥΎ]([θΘκΚξΞπΠσςΣτTφΡχΧψΨ]|\s|$)/u' => 'af$1',
		'/[αΑ][υύΥΎ]/u' => 'av',
		'/[εΕ][υύΥΎ]([θΘκΚξΞπΠσςΣτTφΡχΧψΨ]|\s|$)/u' => 'ef$1',
		'/[εΕ][υύΥΎ]/u' => 'ev',
		'/[οΟ][υύΥΎ]/u' => 'ou',
		'/(^|\s)[μΜ][πΠ]/u' => '$1b',
		'/[μΜ][πΠ](\s|$)/u' => 'b$1',
		'/[μΜ][πΠ]/u' => 'mp',
		'/[νΝ][τΤ]/u' => 'nt',
		'/[τΤ][σΣ]/u' => 'ts',
		'/[τΤ][ζΖ]/u' => 'tz',
		'/[γΓ][γΓ]/u' => 'ng',
		'/[γΓ][κΚ]/u' => 'gk',
		'/[ηΗ][υΥ]([θΘκΚξΞπΠσςΣτTφΡχΧψΨ]|\s|$)/u' => 'if$1',
		'/[ηΗ][υΥ]/u' => 'iu',
		'/[θΘ]/u' => 'th',
		'/[χΧ]/u' => 'ch',
		'/[ψΨ]/u' => 'ps',
		'/[αάΑΆ]/u' => 'a',
		'/[βΒ]/u' => 'v',
		'/[γΓ]/u' => 'g',
		'/[δΔ]/u' => 'd',
		'/[εέΕΈ]/u' => 'e',
		'/[ζΖ]/u' => 'z',
		'/[ηήΗΉ]/u' => 'i',
		'/[ιίϊΙΊΪ]/u' => 'i',
		'/[κΚ]/u' => 'k',
		'/[λΛ]/u' => 'l',
		'/[μΜ]/u' => 'm',
		'/[νΝ]/u' => 'n',
		'/[ξΞ]/u' => 'x',
		'/[οόΟΌ]/u' => 'o',
		'/[πΠ]/u' => 'p',
		'/[ρΡ]/u' => 'r',
		'/[σςΣ]/u' => 's',
		'/[τΤ]/u' => 't',
		'/[υύϋΥΎΫ]/u' => 'i',
		'/[φΦ]/iu' => 'f',
		'/[ωώ]/iu' => 'o'
	);

	$text = preg_replace( array_keys($expressions), array_values($expressions), $text );
	return $text;
}
add_filter('sanitize_title', 'greeklish_permalinks_sanitize_title', 1);