$re = '/[a-zA-ZΆΈ-ώἀ-ῼ]*/';
$str = 'Greek MONOTONIC:
Το γάρ ούν και παρ\' υμίν λεγόμενον, ώς ποτε Φαέθων Ηλίου παίς το του πατρός άρμα ζεύξας δια το μή δυνατός είναι κατά την του πατρός οδόν ελαύνειν τα τ\' επί της γής ξυνέκαυσε και αυτός κεραυνωθείς διεφθάρη, τούτο μύθου μέν σχήμα έχον λέγεται, το δέ αληθές εστι των περί γήν και κατ\' ουρανόν ιόντων παράλλαξις και διά μακρόν χρόνον γιγνομένη των επί γής πυρί πολλώ φθορά.
Greek POLYTONIC:
Τὸ γὰρ οὖν καὶ παρ\' ὑμῖν λεγόμενον, ὥς ποτε Φαέθων Ἡλίου παῖς τὸ τοῦ πατρὸς ἅρμα ζεύξας διὰ τὸ μὴ δυνατὸς εἶναι κατὰ τὴν τοῦ πατρὸς ὁδὸν ἐλαύνειν τὰ τ\' ἐπὶ τῆς γῆς ξυνέκαυσε καὶ αὐτὸς κεραυνωθεὶς διεφθάρη, τοῦτο μύθου μὲν σχῆμα ἔχον λέγεται, τὸ δὲ ἀληθές ἐστι τῶν περὶ γῆν καὶ κατ\' οὐρανὸν ἰόντων παράλλαξις καὶ διὰ μακρὸν χρόνον γιγνομένη τῶν ἐπὶ τῆς γῆς πυρὶ πολλῷ φθορά.
ENGLISH:
For in truth the story that is told in your country as well as ours, how once upon a time Phaethon, son of Helios, yoked his father\'s chariot, and, because he was unable to drive it along the course taken by his father, burnt up all that was upon the earth and himself perished by a thunderbolt,—that story, as it is told, has the fashion of a legend, but the truth of it lies in the occurrence of a shifting of the bodies in the heavens which move round the earth, and a destruction of the things on the earth by fierce fire, which recurs at long intervals.';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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