# 3v4l.org

run code in 200+ php & hhvm versions
```<?php <?php function linear_regression(\$x, \$y) { // calculate number points \$n = count(\$x); // ensure both arrays of points are the same size if (\$n != count(\$y)) { trigger_error("linear_regression(): Number of elements in coordinate arrays do not match.", E_USER_ERROR); } // calculate sums \$x_sum = array_sum(\$x); \$y_sum = array_sum(\$y); \$xx_sum = 0; \$xy_sum = 0; for(\$i = 0; \$i < \$n; \$i++) { \$xy_sum+=(\$x[\$i]*\$y[\$i]); \$xx_sum+=(\$x[\$i]*\$x[\$i]); } // calculate slope //\$m = ((\$n * \$xy_sum) - (\$x_sum * \$y_sum)) / ((\$n * \$xx_sum) - (\$x_sum * \$x_sum)); \$divisor = \$n * \$xx_sum - \$x_sum * \$x_sum; if (\$divisor == 0){ \$m = 0; } else { \$m = ((\$n * \$xy_sum) – (\$x_sum * \$y_sum)) / \$divisor; } // calculate intercept \$b = (\$y_sum - (\$m * \$x_sum)) / \$n; // return result return array("m"=>\$m, "b"=>\$b); } var_dump( linear_regression(array(1, 2, 3, 4, 4), array(1.5, 1.6, 2.1, 3.0, 6)) );```
Output for 5.3.0 - 5.4.21
Parse error: syntax error, unexpected '<' in /in/grREt on line 2
Process exited with code 255.