Rewrite small JavaScript code into PHP

General information for the website: maths
Description of requirements/features: Rewrite small JavaScript code into PHP
Extra notes: The current code is as follows:

0) {
z /= Math.pow( 10, dec );
if (s z) s += 0.5 * z;
else
s = 0;
}

// assure a string
s = "" + s;

// chop neg, if any
var neg = 0;
if (s.charAt(0) == "-") {
neg = 2;
s = s.substring( 1, s.length );
}

// chop exponent, if any
var exp = "";
var e = s.lastIndexOf( "E" );
if (e 0) && ((s.length - dp - 1) 0)
s = "-" + s;

// if not enough width, add spaces IN FRONT
// too many places? tough!
while (s.length < wid)
s = " " + s;

return s
}

function Prb( x ) {
if (x 1) x = 1;
return x;
}

function PosV( x ) {
if (x 1)
t *= x--;
return t;
}

function LnFact( x ) {
// ln(x!) by Stirling's formula
// see Knuth I: 111
if (x <= 1) x = 1;

if (x = 20) return PoissonPD( u, k );
else {
var sum = 0.0, j = 0;
while (j