How can I capitalize the first word of each sentence of a string in PHP?

I am trying to capitalize the first letter of every sentence (after a period, ? or !) I can capitalize the first letter of only the first sentence. Can anyone please help?

$content_trimmed = ucfirst(strtolower($content_trimmed));

Try this

<?php
function capitalize_sentences($text) {
    // Split the text into sentences using regular expression to match ., !, or ?
    $sentences = preg_split('/([.!?]\s*)/', $text, -1, PREG_SPLIT_DELIM_CAPTURE);

    // Loop through the sentences and capitalize the first letter of each
    $result = '';
    foreach ($sentences as $key => $sentence) {
        // If it's an actual sentence (not punctuation), capitalize it
        if ($key % 2 == 0) {
            $result .= ucfirst(strtolower($sentence)); // Capitalize and make the rest lowercase
        } else {
            $result .= $sentence; // Add punctuation back
        }
    }

    return $result;
}

// Example usage
$text = "hello. how are you? i'm fine! how about you?";
echo capitalize_sentences($text);
?>