Please note I don't mean if its meant to be there. I mean if an image cannot be found/located.
For example where the first one below, if monoph.png didnt exist is there a way to display a placeholder?
if ($d == 1 && $h >= 1 && $h < 14) $img = 'img/hosts/monophy.png';
else if ($d == 1 && $h >= 14 && $h < 16) $img = 'img/hosts/mon24.jpg';
else if ($d == 1 && $h >= 16 && $h < 18) $img = 'img/hosts/mon46.jpg';
else if ($d == 1 && $h >= 18 && $h < 20) $img = 'img/hosts/mon68.jpg';
else if ($d == 1 && $h >= 20 && $h < 22) $img = 'img/hosts/mon810.jpg';
else if ($d == 1 && $h >= 22 && $h < 24) $img = 'img/hosts/MON1012.png';
else if ($d == 1 && $h >= 19) $img = 'img/hosts/monophy.png';
else if ($d == 2 && $h < 0) $img = 'img/hosts/monophy.png';