如何在PHP中从数据库中选择一个选定的值

Im trying to make a select that will help me in my "edit user" page. I have this code but I don´t know how to change it so I can load the value selected from the database. This code it´s working...

<div class="form-group">
    <th><label for="text">Tipo Sanguineo:</label></th>
    <td><select class="form-control" id="sangue" name="tipo_sangue">
    <option value="O-" <?php if ($cl_tipo_sangue == "O-") echo 'selected';?> >O-</option>
    <option value="O+" <?php if ($cl_tipo_sangue == "O+") echo 'selected';?> >O+</option>
    <option value="A-" <?php if ($cl_tipo_sangue == "A-") echo 'selected';?> >A-</option>
    <option value="A+" <?php if ($cl_tipo_sangue == "A+") echo 'selected';?> >A+</option>
    <option value="B-" <?php if ($cl_tipo_sangue == "B-") echo 'selected';?> >B-</option>
    <option value="B+" <?php if ($cl_tipo_sangue == "B+") echo 'selected';?> >B+</option>
    <option value="AB-" <?php if ($cl_tipo_sangue == "AB-") echo 'selected';?> >AB-</option>
    <option value="AB+" <?php if ($cl_tipo_sangue == "AB+") echo 'selected';?> >AB+</option>
</select></td>
  </div>

I need to do this with this code:

<?php $dts = DBRead11(); ?>
<select name="diretor_turma" id="diretor_turma" required class="input-field4">
  <?php
    foreach($dts as $option) {
  ?>
    <option value="<?php echo $option['nome']; ?>"><?php echo $option['nome']; ?></option>
  <?php
    }
  ?>
</select>

The code that I need to change is loading the values from the database to the site, and Im not sure how to see the selected one if I load them from the database.

Try this,

<?php $dts = DBRead11(); ?>
<?php $cl_tipo_sangue = "B+"; ?>// here you need to add db value which you saved in DB
<select name="diretor_turma" id="diretor_turma" required class="input-field4">
  <?php
    foreach($dts as $option) {
  ?>
    <option value="<?php echo $option['nome']; ?>" <?php if ($cl_tipo_sangue == $option['nome']) { echo 'selected="selected"'; } ?> ><?php echo $option['nome']; ?></option>
  <?php
    }
  ?>
</select>

Steps:

1) Take an array to save drop down options' id name pairs.

2) Loop over it in the <select> tag for <option>s.

3) Check if selected id is the current iteration id.

4) If yes, add attribute selected="selected" to current <option>

And check in the loop if selected one.

<?php
$bloodGroups = [
'O-' => 'O-',
'O+' => 'O+',
'A-' => 'A-',
'A+' => 'A+',
'B-' => 'B-',
'B+' => 'B+',
'AB-' => 'AB-',
'AB+' => 'AB+'
];
?>
<div class="form-group">
    <th><label for="text">Tipo Sanguineo:</label></th>
    <td><select class="form-control" id="sangue" name="tipo_sangue">
    <?php
    if (! empty($bloodGroups)) {
     foreach ($bloodGroups as $bgid => $bloodGroup) {
      $selected = ($cl_tipo_sangue == $bgid) ? 'selected="selected"' : '';
?>
<option value="<?php echo $bgid;?>" <?php echo $selected;?>><?php echo $bloodGroup;?></option>
<?php
     }
    }
    ?>
</select></td>
  </div>

Using javascript

<?php $dts = DBRead11(); ?>
<select name="diretor_turma" id="diretor_turma" required class="input-field4">
  <?php
    foreach($dts as $option) {
  ?>
    <option value="<?php echo $option['nome']; ?>"><?php echo $option['nome']; ?></option>
  <?php
    }
  ?>
</select>
<script>
    document.querySelector('#diretor_turma').value = '<?= $cl_tipo_sangue ?>'
</script>

You need to fetch the value you saving in database then

 <?php
  $nome = $database_value;

?>
<select name="diretor_turma" id="diretor_turma" required class="input-field4">
  <?php
    foreach($dts as $option) {
  ?>
    <option value="<?php echo $option['nome']; ?>" <?php echo ($option['nome'] == $nome)?'selected':'' ?>><?php echo $option['nome']; ?></option>
  <?php
    }
  ?>
</select>

<select name="diretor_turma" id="diretor_turma" required class="input-field4">
        <?php 
        foreach($dts as $option) {
            $select = (isset($cl_tipo_sangue) && $cl_tipo_sangue == $option['nome'])?"selected = 'selected'":"";?>
            <option value="<?php echo $option['nome']; ?>"  <?php echo $select; ?>><?php echo $option['nome']; ?></option>
        <?php } ?>
</select>