PHP单例模式

<?php
class single{
public $out;
public function a($a){
    $this->out .= $a;
    return $this;
}
public function b($b){
    $this->out .= $b;
    return $this;
}
public function say(){
    echo $this->out.PHP_EOL;
}
public function get(){
    return $this->out;
}
}
$single = new single();
$out = $single->a(‘a‘)->b(‘b‘)->say();
$get = $single->a(‘a‘)->b(‘b‘)->get();
echo $get;

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