Could you point a possible reason a PHP variable is not accepted by an array element?

Hi Experts

Could you point a possible reason a PHP variable is not accepted by an array element?

Accordingly to:

print_r('-------------');
print_r($xxx);  // Has the correct value 
print_r('-------------');

$obj3->professionals = array(
			array('name'=>$xxx,
				  'nickname'=>'',
				  'roles'=>array($papel),
				  //'role'=>array('plantonista'),
				  'internal_id'=>"CONS:".$conselho.'-'.$identificador_interno,
				  'cellphone'=>$reg5['celular_profissional'],
				  'tags'=>array("COOP:".$reg3['cooperativa'],
				  "FUNC:".$reg5['tipo_profissional'],
				  "TIPO_PAGAMENTO:".$tipo_pagamento,
				  "VALOR:R$".$reg5['valor_prof']),
				  "gender"=>$reg5['sexo_profissional'], 
				  "send_invite_when_submit"=>true,
				  'shifts' => $shifts)
			  );						 

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Amazingly $xxx has the correct value but it's not correctly accepted by the array element, another value enters in.

Thanks in advance.