Online PHP editor | refs for aDNbo

<?php $expression = "-11+3*1*4/-6-12"; if (!preg_match('~^-?\d*\.?\d+([*/+-]-?\d*\.?\d+)*$~', $expression)) { echo "invalid expression"; } else { $components = preg_split('~(?<=\d)([*/+-])~', $expression, 0, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE); var_export($components); // ['-11','+','3','*','1','*','4','/','-6','-','12'] while (($index = array_search('*',$components)) !== false) { array_splice($components, $index - 1, 3, $components[$index - 1] * $components[$index + 1]); var_export($components); // ['-11','+','3','*','4','/','-6','-','12'] // ['-11','+','12','/','-6','-','12'] } while (($index = array_search('/', $components)) !== false) { array_splice($components, $index - 1, 3, $components[$index - 1] / $components[$index + 1]); var_export($components); // [-'11','+','-2','-','12'] } while (($index = array_search('+', $components)) !== false) { array_splice($components, $index - 1, 3, $components[$index - 1] + $components[$index + 1]); var_export($components); // ['-13','-','12'] } while (($index = array_search('-', $components)) !== false) { array_splice($components, $index - 1, 3, $components[$index - 1] - $components[$index + 1]); var_export($components); // [-25] } echo current($components); // -25 }