(PECL lapack >= 0.1.0)
Lapack::eigenValues — This function returns the eigenvalues for a given square matrix
$a
   [, array $left
   [, array $right
  ]] )Calculate the eigenvalues for a square matrix, and optionally calculate the left and right eigenvectors.
aThe matrix to calculate the eigenvalues for.
leftOptional parameter - if an array is passed here, it will be filled with the left eigenvectors
rightOptional parameter - if an array is passed here, it will be filled with the right eigenvectors
Returns an array of arrays representing the eigenvalues for the array.
Example #1 Using Lapack::eigenValues():
<?php
 $a = array(
     array(-1.01,   0.86,  -4.60,  3.31,  -4.81  ),
     array( 3.98,   0.53,  -7.04,  5.29,   3.55  ),
     array( 3.30,   8.26,  -3.89,  8.20,  -1.51  ),
     array( 4.43,   4.96,  -7.66, -7.33,   6.18  ),
     array( 7.31,  -6.43,  -6.16,  2.47,   5.58  ),
 );
 $result = Lapack::eigenValues($a);
 ?>