title: php regex replace double backslash with single
body: <p>I do not want to use <code>stripslashes()</code> because I only want to replace "\\" with "\".</p>
  
  <p>I tried <code>preg_replace("/\\\\/", "\\", '2\\sin(\\pi s)\\Gamma(s)\\zeta(s) = i\\oint_C  \\frac{-x^{s-1}}{e^x -1} \\mathrm{d}x');</code></p>
  
  <p>Which to my disapointment returns: <code>2\\sin(\\pi s)\\Gamma(s)\\zeta(s) = i\\oint_C  \\frac{-x^{s-1}}{e^x -1} \\mathrm{d}x</code></p>
  
  <p>Various online regex testers indicate that the above should work. Why is it not?</p>