Belah Ketupat

<?php
function star($length = 10) {
    $characters = ' ';
    $charactersLength = strlen($characters);
    $string = '';
    for ($i = 0; $i < $length; $i++) {
        $string .= $characters;
    }
    return $string;
}

function nilaiTengah($angka){
    $angkaTotal = range(1, $angka);
    if ($angka % 2 == FALSE) {
        return false;
    } else {
        return ((($angka / 2) + 0.5));
    }

}
$panjang = 25;
$nilaiTengah = nilaiTengah($panjang)-1;
$angka = range(1, $panjang);
$output = [];
$lewat_nilai_tengah = 0;
for ($i=1; $i <= $panjang; $i++) {
    $bintang = str_split(star($panjang), "1");
    if ($i == 1 || $i == $panjang) {
        $bintang[$nilaiTengah] = "*";
    } elseif (!isset($awalan) && !isset($akhiran)) {
        $awalan  = ($nilaiTengah-1);
        $akhiran = ($nilaiTengah+1);
        foreach (range($awalan, $akhiran) as $key => $value) {
            $bintang[$value] = "*";
        }
    } elseif ( $i == $nilaiTengah+1 ) {
        $lewat_nilai_tengah = true;
        $awalan  = ($awalan-1);
        $akhiran = ($akhiran+1);
        foreach (range($awalan, $akhiran) as $key => $value) {
            $bintang[$value] = "*";
        }
        $awalan = 0;
        $akhiran = $panjang-1;
    } else {
        if ($lewat_nilai_tengah) {
            $awalan = $awalan+1;
            $akhiran = $akhiran-1;
        } else {
            $awalan  = ($awalan-1);
            $akhiran = ($akhiran+1);
        }
        foreach (range($awalan, $akhiran) as $key => $value) {
            $bintang[$value] = "*";
        }
    }
    $output[] = implode(" ", $bintang);
}
echo (implode(PHP_EOL, $output)).PHP_EOL;