perl to php翻译

Question

如何将此perl子例程转换为PHP函数？

sub disagreement { 
    my $disagreement = 0; 
    my %aggregate =() ; 
    foreach my $item (@_) {$aggregate{$item}++} 
    foreach my $cat_a (keys %aggregate) { 
    foreach my $cat_b (keys %aggregate) { 
     if ($cat_a != $cat_b) {$disagreement += $aggregate{$cat_a} * $aggregate{$cat_b} * &$distance_metric ($cat_a , $cat_b)} 
    } 
    } 
    $disagreement /= @_ * (@_ - 1) ; 
    return ($disagreement) ; 
} 

我这里有一个问题：

foreach my $cat_a (keys %aggregate) { 
    foreach my $cat_b (keys %aggregate) { 
    } 
} 

Answer 1

// &$... is a value reference instead of a value copy, when in doubt use $... 
foreach ($aggregate as $cat_a => &$val_a) { 
    foreach ($aggregate as $cat_b => &$val_b) { 
    if ($cat_a !== $cat_b) $disagreement += $val_a * $val_b ...; 
    } 
} 

Answer 2

foreach my $cat_a (keys %aggregate) 

成为

foreach ($aggregate as $key => $cat_a) 

假设$骨料是一个关联数组。